It's a little handheld Bosch Info Scan tool. I was looking through it but it doesn't look like it's able to communicate with the BCM. Sorry.
SOLVED! No Crank / No Start
- Thread starter Scry0402
- Start date
Just to add to what we have all discussed.
Watched a ScannerDanner video for a quick tip on ways to check if computer is awake by testing a sensor on the 5v reference circuit.
Removed air flow sensor and with the key on was able to verify that there is 5v on that reference circuit.
Also, went inside the car and with the key on, turned the headlights on and put them on bright, the little bright headlight symbol in the instrument cluster did power on when doing that. And if I'm not mistaken, that's usually one of the items that turns on during the "bulb check" during startup.
Thanks again for all the help!
Ryan
Watched a ScannerDanner video for a quick tip on ways to check if computer is awake by testing a sensor on the 5v reference circuit.
Removed air flow sensor and with the key on was able to verify that there is 5v on that reference circuit.
Also, went inside the car and with the key on, turned the headlights on and put them on bright, the little bright headlight symbol in the instrument cluster did power on when doing that. And if I'm not mistaken, that's usually one of the items that turns on during the "bulb check" during startup.
Thanks again for all the help!
Ryan
You might want to de-tab and remove the Green-N-Gold Flat Ribbon Cable running from the BCM Unit over to the Fuse Block and after using some Canned Air to blow out any debris down inside the Black Plastic Female Contact Channels in the Fuse Block, spray some CRC Electrical Solvent down in there and also along BOTH sides of the 12Kt Gold tine contact areas of that Flat Ribbon. After it dries... stick it right back in until it firmly locks in place.
Because the connection between the BCM Unit and the Fuse Block is NOT Solid State... look closely at those tines with a Flashlight and you WILL see a lot of Contact Wear from the Cable wobbling slightly but rapidly back and forth over the years forming significant wear points due to Engine and Body vibrations. Cleaning up this Cable will do no harm and might do as @TJBaker57 suggests in "Waking it Up".
Because the connection between the BCM Unit and the Fuse Block is NOT Solid State... look closely at those tines with a Flashlight and you WILL see a lot of Contact Wear from the Cable wobbling slightly but rapidly back and forth over the years forming significant wear points due to Engine and Body vibrations. Cleaning up this Cable will do no harm and might do as @TJBaker57 suggests in "Waking it Up".
good test on the headlights... that shows that at some point, there is good communication to the IPC and that the light (at least one) is functional. I haven't had time to trace things further yet but will.
Although a test light is handy / useful, it does not provide all information about what's happening in circuit points. As you pointed out things like data circuits can't be readily checked with it. In addition, circuit resistances are worth knowning not so much as an absolute value but relative to other circuit checks. These are done with a meter. These will allow you to measure the output pin of the PCM circuit that is controlling the ground send circuit. This checks needs to be down with no power (battery disconnected).... checking the resistance to ground on pin 39 of the pcm (assuming 4.2). Similar checks should also be done on the PNP and crank voltage pins at the pcm.
Further at the BCM, check the state of ign 0,1,3 (pins A18,19,20 along accessory (b15)... in terms of key position (it can be done with test light).
Based on my "read", I would track on IGN1 signals. This needs to get to pcm, the cluster and the BCM.
Although a test light is handy / useful, it does not provide all information about what's happening in circuit points. As you pointed out things like data circuits can't be readily checked with it. In addition, circuit resistances are worth knowning not so much as an absolute value but relative to other circuit checks. These are done with a meter. These will allow you to measure the output pin of the PCM circuit that is controlling the ground send circuit. This checks needs to be down with no power (battery disconnected).... checking the resistance to ground on pin 39 of the pcm (assuming 4.2). Similar checks should also be done on the PNP and crank voltage pins at the pcm.
Further at the BCM, check the state of ign 0,1,3 (pins A18,19,20 along accessory (b15)... in terms of key position (it can be done with test light).
Based on my "read", I would track on IGN1 signals. This needs to get to pcm, the cluster and the BCM.
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Mooseman
Moderator
The fact that the gauge cluster is not coming fully alive still tells me it's a power or ground issue. Did you check the grounds? G102, which is located near the underhood fuse block, is responsible for a lot of systems, including the IPC, BCM and Theft Deterrent.
The PCM itself is getting good power and ground since it's able to start and run the engine when jumping the starter relay.
Beyond that, without a high end scanner, I think we're just chasing our tails here.
The PCM itself is getting good power and ground since it's able to start and run the engine when jumping the starter relay.
Beyond that, without a high end scanner, I think we're just chasing our tails here.
@budwich
I hope the table I provided help understand voltages based on key position.
I've got a little multi-meter I could use to check resistance. Can I just verify with you exactly which pins under which connectors to test.
You are right, it is a 4.2L.
The only Pin 39 that seems to be used is under C2 and is for the high side of the camshaft solenoid actuator.
The other Pins you referenced were for the PNP Switch which appears to be Pin 29 on C1 and the crank voltage which is Pin 31 on C1.
Just an fyi-the high beam lamp illimunates on cluster no matter if key is off or on. Normal behavior.
@MRRSM
All fuses in rear fuse box check out fine. Any that didn't have power with the key in run I pulled out to visually inspect.
All fuses correlated to BCM had power.
Thanks,
Ryan
I hope the table I provided help understand voltages based on key position.
I've got a little multi-meter I could use to check resistance. Can I just verify with you exactly which pins under which connectors to test.
You are right, it is a 4.2L.
The only Pin 39 that seems to be used is under C2 and is for the high side of the camshaft solenoid actuator.
The other Pins you referenced were for the PNP Switch which appears to be Pin 29 on C1 and the crank voltage which is Pin 31 on C1.
Just an fyi-the high beam lamp illimunates on cluster no matter if key is off or on. Normal behavior.
@MRRSM
All fuses in rear fuse box check out fine. Any that didn't have power with the key in run I pulled out to visually inspect.
All fuses correlated to BCM had power.
Thanks,
Ryan
yep, i screwed up on the start ground, I gave you the 5.3 location.... on the 4.2, pin 48. sorry, my eyes don't see so well in the morning... especially when I am going across screens and computers and blame the eyes but its more likely the brain not translating right.
Anyway, it unlikely to be a ground / power issue directly, its more likely a wiring issue between things as I do believe your key is working but not getting the signals to where they need to be.
One more thing.... related to my earlier suggestion, is check fuse 22 for the ign1... not so much the fuse but the connections in and around the blades to ensure that it happening.
Anyway, it unlikely to be a ground / power issue directly, its more likely a wiring issue between things as I do believe your key is working but not getting the signals to where they need to be.
One more thing.... related to my earlier suggestion, is check fuse 22 for the ign1... not so much the fuse but the connections in and around the blades to ensure that it happening.
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If it turns out that the Under-Hood Power Distribution Center winds up Center Stage as a Suspect... eBay has quite a few 2002-2003 Units available for not too much Bread:
2003 Trailblazer Fuse Block for sale | eBay
Get the best deals for 2003 Trailblazer Fuse Block at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!
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Mooseman
Moderator
At the relay socket? The starter motor should run only for as long as it's being jumped by you. It's the PCM that does the thing where it keeps cranking until it starts even though you let go of the key after flicking it to start. The PCM does that through the - signal wire to the starter relay.
So you were able to confirm that the PCM is receiving the + signal from the ignition switch when in the START position?
I'd still be concentrating on why the cluster is not powering up completely. Other systems like the BCM and Theft deterrent may also be affected.
Another thing... you have check your accessory position on your switch whereby only the battery light should come on the dash. This position is just before the run.
@MRRSM @budwich @Mooseman
Basically I've gotten so knee deep into this problem that something that's so basic has been overlooked by me. And I feel like a complete idiot because of it.
When jumping the Trailblazer using the jumper wire method with the key in the on position, the vehicle should continue running until I physically go inside the cabin and turn the key off assuming everything within the PCM was operational.
Right now, this is not what happens. When I jump it using the jump wire and it turns over and fires, it'll only run for a second or two before it dies. It doesn't stay running on its own.
I pulled each connector to the PCM off this past Sunday and tested any socket on each connector that was tied to the ignition or was tied to 12v battery power with a small wire and my test light. All sockets and each connector that were supposed to have power with the key on did.
The fact this vehicle will not stay running, and I've verified there is ignition power and there is crank voltage, and there is voltage to the PNP socket as well tells me this thing has a bad PCM.
I hate to make that conclusion, but the fact the PCM is supposed to communicate to the ICP and we can't get that to go through the bulb check on startup and when the key is on and it won't stay running on its own.
One lasts basic suggestion, I've kept a battery charger on the battery throughout this process, ranging in voltage from 11.9 to 12.6 depending on how long I've got doors open, lights on, etc...
Could a bad battery be the culprit? I don't think so though, because I don't think this would explain why the dash doesn't go through the "bulb check" when the key is turned over.
Thanks,
Ryan
Basically I've gotten so knee deep into this problem that something that's so basic has been overlooked by me. And I feel like a complete idiot because of it.
When jumping the Trailblazer using the jumper wire method with the key in the on position, the vehicle should continue running until I physically go inside the cabin and turn the key off assuming everything within the PCM was operational.
Right now, this is not what happens. When I jump it using the jump wire and it turns over and fires, it'll only run for a second or two before it dies. It doesn't stay running on its own.
I pulled each connector to the PCM off this past Sunday and tested any socket on each connector that was tied to the ignition or was tied to 12v battery power with a small wire and my test light. All sockets and each connector that were supposed to have power with the key on did.
The fact this vehicle will not stay running, and I've verified there is ignition power and there is crank voltage, and there is voltage to the PNP socket as well tells me this thing has a bad PCM.
I hate to make that conclusion, but the fact the PCM is supposed to communicate to the ICP and we can't get that to go through the bulb check on startup and when the key is on and it won't stay running on its own.
One lasts basic suggestion, I've kept a battery charger on the battery throughout this process, ranging in voltage from 11.9 to 12.6 depending on how long I've got doors open, lights on, etc...
Could a bad battery be the culprit? I don't think so though, because I don't think this would explain why the dash doesn't go through the "bulb check" when the key is turned over.
Thanks,
Ryan
you could be right... but I am not sure you can draw the conclusion conclusively... 
The engine should run IF all systems are functionally OK and that indeed they are getting their "fair share" of signals / powering accordingly.
Depending on how much more time you want to spend and also the availability of a "spare pcm", it might be worth that direction as a "quick get out of jail for ... while some money".
I am still of the thought that there is a wire path not completely happy to / thru some component areas including the fuse box as was mrrsm. The reason for this is the "one time start with dash lights".
The engine should run IF all systems are functionally OK and that indeed they are getting their "fair share" of signals / powering accordingly.Depending on how much more time you want to spend and also the availability of a "spare pcm", it might be worth that direction as a "quick get out of jail for ... while some money".
I am still of the thought that there is a wire path not completely happy to / thru some component areas including the fuse box as was mrrsm. The reason for this is the "one time start with dash lights".
As a recap, you have confirmed signals at the pcm, but have not checked signals at the BCM or the IPC. Those modules also come into play with the things you are and aren't seeing.
Pardon me for any spelling errors, responding from my phone.
I know it's rare, extremely rare, but I'm just left with what else could it possibly be?
@budwich - you're right, this is true. But to add to this, here's what we do know:
On midnight Friday all the bulbs that would normally come on during bulb check were on after key was left in the run position for an hour or two. At the connector behind IPC I have to believe connections are good cause they were 3 days ago when it randomly worked. It seems the signal just isn't being sent and that there's nothing wrong with any wiring there.
As for the BCM, I'm not 100% on everything it controls, but I know I've got a lot of the functions it does control. Headlight switch works, dimmer to dash lights works, cabin lights work, all headlights/taillights license plate light works. Power windows work, even the compass located in the rest view mirror works. Power mirrors work, 4-way work, power seats work. Wipers front and rear work. Horn works.
We also know that the bright light symbol on dash illuminates when high beams are activated.
I know all fuses under his fuse block are good. I know all fusesn in rear fuse block are good.
I know each PCM connector is showing voltage for anything ignition related, 12v battery related.
I know the crank first under his has 12v power when turning key to crank.
I also know I can't keep the vehicle running when jumping it in fuse block with key in on position.
I know these systems are touchy and complicated, but after all this what more could it possibly be given all what we know.
The fact those bulbs don't come on when key is turned to run, and I know there's power at PCM, just really has me down the road of a computer issue.
Theres several of these no crank videos online for these GM trucks, but I haven't seen one where you can't even get the bulb check to occur. And the only one that I've seen that the bulb check didn't happen was when nothing worked after a guy put in a new battery that turned out to be bad.
Just really kind of getting to my wits end with it cause based on all that I can do I know power is getting to where it needs to be based on wiring schematics.
I know it's rare, extremely rare, but I'm just left with what else could it possibly be?
@budwich - you're right, this is true. But to add to this, here's what we do know:
On midnight Friday all the bulbs that would normally come on during bulb check were on after key was left in the run position for an hour or two. At the connector behind IPC I have to believe connections are good cause they were 3 days ago when it randomly worked. It seems the signal just isn't being sent and that there's nothing wrong with any wiring there.
As for the BCM, I'm not 100% on everything it controls, but I know I've got a lot of the functions it does control. Headlight switch works, dimmer to dash lights works, cabin lights work, all headlights/taillights license plate light works. Power windows work, even the compass located in the rest view mirror works. Power mirrors work, 4-way work, power seats work. Wipers front and rear work. Horn works.
We also know that the bright light symbol on dash illuminates when high beams are activated.
I know all fuses under his fuse block are good. I know all fusesn in rear fuse block are good.
I know each PCM connector is showing voltage for anything ignition related, 12v battery related.
I know the crank first under his has 12v power when turning key to crank.
I also know I can't keep the vehicle running when jumping it in fuse block with key in on position.
I know these systems are touchy and complicated, but after all this what more could it possibly be given all what we know.
The fact those bulbs don't come on when key is turned to run, and I know there's power at PCM, just really has me down the road of a computer issue.
Theres several of these no crank videos online for these GM trucks, but I haven't seen one where you can't even get the bulb check to occur. And the only one that I've seen that the bulb check didn't happen was when nothing worked after a guy put in a new battery that turned out to be bad.
Just really kind of getting to my wits end with it cause based on all that I can do I know power is getting to where it needs to be based on wiring schematics.
yes BUT.... what you don't know is how the "all bulbs" test is activated. You make the assumption that it is done from the PCM. That may be true... but it does not have to be true. The IPC has some of its own brains. It only needs a signal to do this.... IGN 1 maybe especially if it knows about "transistions" meaning if there is power going to the IPC, it has "conscience". Then, if it monitors a signal, it may readily do a "reset" / "all bulbs" test if it see a change in that signal. Of course, I know nothing of this as this is just a guess from my "reads".
Further, when you say you have no DIC... how do you know that?
Further, when you say you have no DIC... how do you know that?
I should add, the things I know I don't have are:
The bulb check lights when key is turned to crank
Blower motor won't turn on
No crank
The bulb check lights when key is turned to crank
Blower motor won't turn on
No crank
When the vehicle started on Friday, the DIC panel illuminated and was completely functional from buttons on steering wheel.
I should also note I have seen videos where a GM truck is able to run despite the gauge cluster bring completely dead, meaning no back lights, no gauges activated, no DIC, no nothing.
That tells me that in those circumstances despite gauge cluster bring completely dead, the vehicle can still crank and run.
Since the computer from what we know powers that bulb check at startup, and the computer sends the ground signal to starter relay and neither of those two things are happening in addition to when vehicle is jumped it only runs for a second or two before stalling points me back to computer.
I'm happy to do more troubleshooting though, just thought it'd be good to recap what we do know and don't know.
I could put all those items into a table to better help organize a further plan of attack.
Again, just common sense here, but if computer was communicating with IPC at the very least the volt meter and fuel gauge needle should move.
I should also note, the blinker lights on IPC work, as well as the turn signal lever and 4-way flashers switch.
I should also note I have seen videos where a GM truck is able to run despite the gauge cluster bring completely dead, meaning no back lights, no gauges activated, no DIC, no nothing.
That tells me that in those circumstances despite gauge cluster bring completely dead, the vehicle can still crank and run.
Since the computer from what we know powers that bulb check at startup, and the computer sends the ground signal to starter relay and neither of those two things are happening in addition to when vehicle is jumped it only runs for a second or two before stalling points me back to computer.
I'm happy to do more troubleshooting though, just thought it'd be good to recap what we do know and don't know.
I could put all those items into a table to better help organize a further plan of attack.
Again, just common sense here, but if computer was communicating with IPC at the very least the volt meter and fuel gauge needle should move.
I should also note, the blinker lights on IPC work, as well as the turn signal lever and 4-way flashers switch.
BUT... I think you are still making some assumptions.... note: perhaps IF the cluster has "knowledge" that NO ignition has happened (ie. no voltage), then turning on some of those indicators should NOT happen as it does not make sense to light things / work things that use power for nothing. Again just a counter to your view.
One side note: the BCM controls lighting of headlight brights indicator.
One side note: the BCM controls lighting of headlight brights indicator.
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Hold it... I missed this... I am slow. You are saying you not getting "the check bulb sequence" on the IPC when you attempt a crank? That is not correct operation.
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As we have been throwing around, there is an IGN 1 fuse / lead going to the IPC. Pull the fuse. Make sure you know which side of the fuse block is the source and which side is the IPC panel. Pull the fuse. Take a fused jumper and run 12v to the IPC side of things. What happens?
forget the ign 1 at the cluster... the SES light is run by this so it is there.
The last checks that you might do is at the BCM to ensure it is seeing appropriate signals / voltages at states. IF so, that potentially only leaves the PCM failure as you are leaning towards.
One other thing... in "normal run", the battery light should not be on. This might be significant if the battery is insufficient to run things properly especially the PCM.
The last checks that you might do is at the BCM to ensure it is seeing appropriate signals / voltages at states. IF so, that potentially only leaves the PCM failure as you are leaning towards.
One other thing... in "normal run", the battery light should not be on. This might be significant if the battery is insufficient to run things properly especially the PCM.
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Reading thru all this, and i feel like one thing has been overlooked. VATS. He indicated earlier that the ignition lock had been replaced by some aftermarket unit. He also talked about leaving the key on for a long while, and all of the IPC lights came on, and it also started. Why does this sound to me like it was in the middle of a VATS relearn that got interrupted? Is there a VATS module on the outside of the ignition switch? How many keys do you have for this truck? Are any of them OEM VATS key, or are they all aftermarket unknowns? Do you know how to perform a VATS relearn? I know its a timely process...
Mooseman
Moderator
The IPC is not getting power. The bulb check is done internally by the IPC itself. The PCM is not involved with that. If you don't believe me, watch this when he powers it without a PCM.
Since there is no power to the IPC, I am still suspicious of power or ground not getting to other modules, like VATS and the HVAC since you say the blower doesn't work.
Since there is no power to the IPC, I am still suspicious of power or ground not getting to other modules, like VATS and the HVAC since you say the blower doesn't work.
If @Scry0402 is correct, the Tech 2 would be THE Scanner to have right now. Using it in concert with this excerpt information from the PDF in Post #12 would help in determining if the PCM needs replacement:
" 3. If SI diagnostics continue to lead to PCM replacement even though it was recently replaced for the same concern, the PCM may have internal damage due to a shorted driver circuit or low reference circuit. Once this PCM does not contain internal fault protection, internal PCM damage may occur if a high side driver circuit/component shorts to ground, or if a low side driver circuit/component or low reference circuit shorts to power.
If internal PCM damage is suspected, operate all PCM drivers with a Tech 2 to ensure proper operation. If a PCM driver exhibits abnormal operation, inspect the related driver circuit/component for a short and repair as necessary. If normal driver operation is noted, inspect all driver circuits/components for shorts, especially near the PCM as described in steps 1 and 2 above.
If there is no problem found with any of the drivers or driver circuits but internal PCM damage is still suspected, determine if the PCM is setting high voltage DTCs for components in one of the groups below. If the PCM is setting high voltage DTCs for only 1 of the 3 groups, the internal PCM damage is most likely due to a component in this group having its low reference circuit shorted to power. "
" 3. If SI diagnostics continue to lead to PCM replacement even though it was recently replaced for the same concern, the PCM may have internal damage due to a shorted driver circuit or low reference circuit. Once this PCM does not contain internal fault protection, internal PCM damage may occur if a high side driver circuit/component shorts to ground, or if a low side driver circuit/component or low reference circuit shorts to power.
If internal PCM damage is suspected, operate all PCM drivers with a Tech 2 to ensure proper operation. If a PCM driver exhibits abnormal operation, inspect the related driver circuit/component for a short and repair as necessary. If normal driver operation is noted, inspect all driver circuits/components for shorts, especially near the PCM as described in steps 1 and 2 above.
If there is no problem found with any of the drivers or driver circuits but internal PCM damage is still suspected, determine if the PCM is setting high voltage DTCs for components in one of the groups below. If the PCM is setting high voltage DTCs for only 1 of the 3 groups, the internal PCM damage is most likely due to a component in this group having its low reference circuit shorted to power. "
Thanks for the all the additional responses all. I apologize, I was away from the thread today. Had the wife's birthday and it was the first 70 degree day we've had here in Minnesota since probably last September.
I didnt check this beforehand, but a buddy of mine came over who works for a local repair shop in our town.
We checked all IGN 0 & IGN 1 wires connected at the PCM, all have voltage. The PNP wire at the PCM has 12v. The crank wire at the PCM has 12v when key cylinder is turned.
The Black/Yellow wire on Pin 48 at C1 does not signal when the vehicle cranks.
We jumped it, it ran for 2 seconds then died. So it obviously has no ignition signal.
We also looked inside PCM to see if there were any noticeable burns.
He's baffled, we tried tracing schematics to see if there's anything that was missed. But there isn't. The PCM is getting Ignition, it's getting crank, it's just not sending that signal on out of 48 to starter relay. And still no dash lights coming on when key is in run position.
Let me take this message by message.
@TollKeeper - I've got two keys, one factory, one aftermarket. Looks to be factory keyfob. The OEM key goes into key cylinder but won't turn it. The aftermarket key goes and turns it. I've got to be honest, I'm not sure what VATS is. I'll have to look to see what a VATS module is. If you have further insight I'd appreciate it. I'll do some research on that tonight.
@Mooseman - Thanks for that video, obviously the IPC puts those lights on itself. WTF is wrong with this Trailblazer I have.
@budwich - Thanks for the further suggestions. I'll have to try that tomorrow.
@MRRSM - My auto technician buddy and I pulled PCM from vehicle. Opened it up, inspected it closely for any signs of surging or burns. Nothing. Put it back together and installed it back on vehicle.
Thanks,
Ryan
I didnt check this beforehand, but a buddy of mine came over who works for a local repair shop in our town.
We checked all IGN 0 & IGN 1 wires connected at the PCM, all have voltage. The PNP wire at the PCM has 12v. The crank wire at the PCM has 12v when key cylinder is turned.
The Black/Yellow wire on Pin 48 at C1 does not signal when the vehicle cranks.
We jumped it, it ran for 2 seconds then died. So it obviously has no ignition signal.
We also looked inside PCM to see if there were any noticeable burns.
He's baffled, we tried tracing schematics to see if there's anything that was missed. But there isn't. The PCM is getting Ignition, it's getting crank, it's just not sending that signal on out of 48 to starter relay. And still no dash lights coming on when key is in run position.
Let me take this message by message.
@TollKeeper - I've got two keys, one factory, one aftermarket. Looks to be factory keyfob. The OEM key goes into key cylinder but won't turn it. The aftermarket key goes and turns it. I've got to be honest, I'm not sure what VATS is. I'll have to look to see what a VATS module is. If you have further insight I'd appreciate it. I'll do some research on that tonight.
@Mooseman - Thanks for that video, obviously the IPC puts those lights on itself. WTF is wrong with this Trailblazer I have.
@budwich - Thanks for the further suggestions. I'll have to try that tomorrow.
@MRRSM - My auto technician buddy and I pulled PCM from vehicle. Opened it up, inspected it closely for any signs of surging or burns. Nothing. Put it back together and installed it back on vehicle.
Thanks,
Ryan
christo829
Member
"We jumped it, it ran for 2 seconds then died. So it obviously has no ignition signal."
This sounds like a security system issue. There's no telling what may have been screwed up by the installation and then subsequent removal of that aftermarket security system.
I'd consider going back through all those cut and spliced wires under the dash and redo them with solder and heat shrink. I've had crimp splices fail to properly complete a circuit even when they were crimped down as much as the crimp tool could get them.
The lack of lights sounds a lot like what happened after my wiring bundle got rodent chewed. Nothing wrong with the PCM, but the data couldn't get where it needed to go. The problem is that if you're not getting all the lights, you wouldn't know if the security light was supposed to be coming on to indicate a problem or not.
Good Luck-
Chris
This sounds like a security system issue. There's no telling what may have been screwed up by the installation and then subsequent removal of that aftermarket security system.
I'd consider going back through all those cut and spliced wires under the dash and redo them with solder and heat shrink. I've had crimp splices fail to properly complete a circuit even when they were crimped down as much as the crimp tool could get them.
The lack of lights sounds a lot like what happened after my wiring bundle got rodent chewed. Nothing wrong with the PCM, but the data couldn't get where it needed to go. The problem is that if you're not getting all the lights, you wouldn't know if the security light was supposed to be coming on to indicate a problem or not.
Good Luck-
Chris
Mooseman
Moderator
It's probably dying because there is no fuel pressure. When VATS is activated to disable a vehicle, it prevents cranking and also doesn't activate the fuel pump. So probably the PCM is expecting the signal from VATS to go ahead but it isn't so won't allow it to start and run. If the VATS module is not powering up (same as the IPC), it might not be able to send that.
Another possibility is that the IPC is defective and screwing up the CANBUS, preventing the VATS from giving the go ahead to the PCM. I would take the dash apart, take the IPC out and check that the power is getting to it. You can leave it unplugged and try to start it. Normally, it would still start without it.
It's not the first time that a module or something on the CANBUS would screw things up.
Another possibility is that the IPC is defective and screwing up the CANBUS, preventing the VATS from giving the go ahead to the PCM. I would take the dash apart, take the IPC out and check that the power is getting to it. You can leave it unplugged and try to start it. Normally, it would still start without it.
It's not the first time that a module or something on the CANBUS would screw things up.
@Mooseman - I was doing a bit of reading this evening, and I'd like to get your assessment of this.
So I'm just going to focus on the instrument panel. According to All Data DIY, here's some information about operation of the instrument cluster. Specifically, I'm interested in the fuel gage in the PRND321 Display. Here's what It says:
FUEL GAGE
The IPC displays the fuel level as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the fuel level percent. The fuel gage defaults to empty if:
PRND321 DISPLAY
The IPC displays the selected gear position as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the gear position. The PRND321 display blanks if:
So right now, I've got a fuel gauge that defaults to empty, but a PRND321 display that is on.
The instrument panel cluster only has one class 2 data pin on it's connector. The PRNDL321 and the Fuel Gauge both need to have the key in the run position to operate. Both require
So the question is, how is it possible that I've got a PRNDL321 display appearing but no reading of the fuel gauge? I understand that it's possible that the transmission range switch circuit for the PRNDL and fuel level sensor circuit are two separate circuits. But if those two items are on the same circuit then they both should offer a reading if the PCM isn't malfunctioning.
I was doing some snooping, but I couldn't find what precise circuits these two items are on.
Additionally, I have no effing clue why those indicator lights on the instrument cluster won't come on if all they require is 12v at when the key is turned to run then they should be coming on because obviously the dash has Battery + and Ignition due to the PRNDL321 and Service Engine Soon lights being lit. The schematic says though that the indicator lights also need Class 2 Data, but my assumption is that would be to get them to come on after startup. However, if they need class 2 data at startup, that would come from the DLC which would get it's signal from the PCM. Their schematics are below.
Last thing would be that cluster as you stated is messed up, screwing with the CANBUS, etc....
So I'm just going to focus on the instrument panel. According to All Data DIY, here's some information about operation of the instrument cluster. Specifically, I'm interested in the fuel gage in the PRND321 Display. Here's what It says:
FUEL GAGE
The IPC displays the fuel level as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the fuel level percent. The fuel gage defaults to empty if:
- The PCM detects a malfunction in the fuel level sensor circuit.
- The IPC detects a loss of class 2 communications with the PCM.
PRND321 DISPLAY
The IPC displays the selected gear position as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the gear position. The PRND321 display blanks if:
- The PCM detects a malfunction in the transmission range switch circuit.
- The IPC detects a loss of class 2 communications with the PCM.
So right now, I've got a fuel gauge that defaults to empty, but a PRND321 display that is on.
The instrument panel cluster only has one class 2 data pin on it's connector. The PRNDL321 and the Fuel Gauge both need to have the key in the run position to operate. Both require
So the question is, how is it possible that I've got a PRNDL321 display appearing but no reading of the fuel gauge? I understand that it's possible that the transmission range switch circuit for the PRNDL and fuel level sensor circuit are two separate circuits. But if those two items are on the same circuit then they both should offer a reading if the PCM isn't malfunctioning.
I was doing some snooping, but I couldn't find what precise circuits these two items are on.
Additionally, I have no effing clue why those indicator lights on the instrument cluster won't come on if all they require is 12v at when the key is turned to run then they should be coming on because obviously the dash has Battery + and Ignition due to the PRNDL321 and Service Engine Soon lights being lit. The schematic says though that the indicator lights also need Class 2 Data, but my assumption is that would be to get them to come on after startup. However, if they need class 2 data at startup, that would come from the DLC which would get it's signal from the PCM. Their schematics are below.
Last thing would be that cluster as you stated is messed up, screwing with the CANBUS, etc....
Attachments
Is your battery light still on? IF so, can you make it go out?
As far as comms, the "center of the universe" is the BCM not the PCM.
As far as comms, the "center of the universe" is the BCM not the PCM.
ANY Shorted Module anywhere on the Single Wire Class 2 network can present with bizarre artifacts and system-wide failures. So it follows on that with the image posted by @TJBaker57 of the CANBUS "Splice Comb" and the last suggestion made by @Mooseman... there is a simple way to Diagnose the Low Voltage (0-7 Volts DC) Class 2 Network and ALL Modules by first pulling the jagged Metal Plug out of the end of the Splice Pack under the Driver's Side Dashboard and with the Ignition Key turned ON ... use a DVOM or DMM to test the Voltage on each individual wire within the Splice Pack.
If you Test and Read any Voltage above 7 Volts DC or a straight 12 Volts DC on any of the Modules Class 2 Wires in the Pack, then you'll have found a "Low Voltage Short To Power" problem. The same will apply for the Aft Cabin Class 2 Network Splice Pack where it is hidden under the Right Rear Passenger Seat under a small Carpet Flap.
Now even though this Video deals with a raft of UXXXX Codes that lead to a dead shorted Module on the floor of the Rear Driver's Side of the Vehicle... Mr. Will Robinson shows you the Layout-Pin-Out of the Splice Packs and which wires go to all of the in-dwelling Modules. None of these wires should ever carry 12 Volts DC, so for the sake of 'the process of elimination', the VOP does a very good job of explaining his diagnostic work to the Viewer:
If you Test and Read any Voltage above 7 Volts DC or a straight 12 Volts DC on any of the Modules Class 2 Wires in the Pack, then you'll have found a "Low Voltage Short To Power" problem. The same will apply for the Aft Cabin Class 2 Network Splice Pack where it is hidden under the Right Rear Passenger Seat under a small Carpet Flap.
Now even though this Video deals with a raft of UXXXX Codes that lead to a dead shorted Module on the floor of the Rear Driver's Side of the Vehicle... Mr. Will Robinson shows you the Layout-Pin-Out of the Splice Packs and which wires go to all of the in-dwelling Modules. None of these wires should ever carry 12 Volts DC, so for the sake of 'the process of elimination', the VOP does a very good job of explaining his diagnostic work to the Viewer:
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Mooseman
Moderator
The fact remains that it doesn't go through the bulb check which means either power is not getting to it or it's defective. If power is not getting to it, the question is why?
@budwich - Battery light is a constant on. In no position with the key in does it ever go out. And as for the key positions in your previous post, when turning the key over, battery light illuminates when the key is turned the ACC, then the "SES" light comes on when key is moved to run.
@MRRSM - Thanks for that video. When we jumped it yesterday and it only ran briefly and died, so many guys are pointing to a security problem and not a ignition problem. Based on that, I'd have to assume this vehicle is equipped with immobilizer.
I'll attach the Data Link Connector schematic again and I was hoping you (or anyone) might be able to help me make out what's going on a little more.
So on that schematic a PPL wire comes out of the DLC and is spliced with a white wire at #S232. That white wire continues on to connector C201 in the C3 location. On the back side it travels to a "Theft Deterrent Module", then that module comes back around to C201 and connects in the C3 spot. And then what happens after that? Is it just the straight yellow wire that leads back to PCM, or does it connect with the BCM at that C3 location and then both go to the PCM? That's one area of this schematic I'm left confused about.
Back to the PPL wire, after it's spliced at #S232 it continues on to Splice Pack 205, the same connector the guy in the video you shared initially began testing to bring modules online.
And it looks like at that splice pack there's modules for Hvac, there's also a wire that carries data up to the instrument cluster, so yes, we will definitely be getting on this today with a multimeter to test voltages of each individual pin.
@Mooseman - Hate making assumptions...but wouldn't it be fair to say that the orange wire coming in from Battery+ should be providing power because the PRND321 is illuminated? And along the same vein, wouldn't it be fair to say that the ignition wire coming in also has power because the "Service Engine Soon" light illuminates and all it needs to come on is the power from that ignition wire and signal from the PCM.
That would basically only leave a defective dash as the culprit to not allowing the other indicator lights to come on at startup.
Either way, I'll be tearing the dash apart today and testing that as well.
Thanks,
Ryan
@MRRSM - Thanks for that video. When we jumped it yesterday and it only ran briefly and died, so many guys are pointing to a security problem and not a ignition problem. Based on that, I'd have to assume this vehicle is equipped with immobilizer.
I'll attach the Data Link Connector schematic again and I was hoping you (or anyone) might be able to help me make out what's going on a little more.
So on that schematic a PPL wire comes out of the DLC and is spliced with a white wire at #S232. That white wire continues on to connector C201 in the C3 location. On the back side it travels to a "Theft Deterrent Module", then that module comes back around to C201 and connects in the C3 spot. And then what happens after that? Is it just the straight yellow wire that leads back to PCM, or does it connect with the BCM at that C3 location and then both go to the PCM? That's one area of this schematic I'm left confused about.
Back to the PPL wire, after it's spliced at #S232 it continues on to Splice Pack 205, the same connector the guy in the video you shared initially began testing to bring modules online.
And it looks like at that splice pack there's modules for Hvac, there's also a wire that carries data up to the instrument cluster, so yes, we will definitely be getting on this today with a multimeter to test voltages of each individual pin.
@Mooseman - Hate making assumptions...but wouldn't it be fair to say that the orange wire coming in from Battery+ should be providing power because the PRND321 is illuminated? And along the same vein, wouldn't it be fair to say that the ignition wire coming in also has power because the "Service Engine Soon" light illuminates and all it needs to come on is the power from that ignition wire and signal from the PCM.
That would basically only leave a defective dash as the culprit to not allowing the other indicator lights to come on at startup.
Either way, I'll be tearing the dash apart today and testing that as well.
Thanks,
Ryan
Attachments
Without knowing what the precise Alarm Installation Hardware looks like... the closest thing I can come up with for a Wiring Conversion Schematic and Wire Exchange Table for the 2002-2009 Trailblazers and Envoys is THIS One:
JFTHOI...
Look around under the Driver's Side Dash Panel near to or just above the Rocker Panel and Door Post in the areas of the Plastic Fascia for a Very Small Toggle Switch that many Alarm Installers include as an Alarm By-Pass.
It is usually placed within the Driver's Reach and would be very easy to overlook if the small mounting Lock-Washer and Slip Nut Hardware had loosened up enough to allow it to fall through a small mounting hole drilled into one of the adjacent Plastic Fascia Covers. If there is one there... Flip it to the opposite position and try to start the SUV.
2002-2007 Chevrolet Trailblazer Vehicle Wiring Chart and Diagram
Commando Car Alarms offers free wiring diagrams for your 2002-2007 Chevrolet Trailblazer. Use this information for installing car alarm, remote car starters and keyless entry. View our complete listing of wiring diagrams for your Chevrolet Trailblazer.
www.commandocaralarms.com
JFTHOI...
Look around under the Driver's Side Dash Panel near to or just above the Rocker Panel and Door Post in the areas of the Plastic Fascia for a Very Small Toggle Switch that many Alarm Installers include as an Alarm By-Pass.
It is usually placed within the Driver's Reach and would be very easy to overlook if the small mounting Lock-Washer and Slip Nut Hardware had loosened up enough to allow it to fall through a small mounting hole drilled into one of the adjacent Plastic Fascia Covers. If there is one there... Flip it to the opposite position and try to start the SUV.
Quote: "
Battery light is a constant on. In no position with the key in does it ever go out. And as for the key positions in your previous post, when turning the key over, battery light illuminates when the key is turned the ACC, then the "SES" light comes on when key is moved to run. "
thanks for the information. just to clarify a bit more, "with the key in", the light is on, but if you remove the key, is the light still on?
Key detection is a function of the BCM.
You might have multiple problems (especially if wiring was basterdized). In terms of the dash, if and when you get access to the IPC, you can likely follow the same "power test" as shown in the video to check the response of the IPC without any connection to the bus.
One other thing... in your "short times of running", did you notice what's up with the dash and in particular, whether there is a theft indicator lit? related to this, you can potentially overcome some of this, perhaps, by also jumping power directly to the fuel pump so that it can't be disabled IF that is the case. IF the vehicle runs in this mode, then you have narrowed down what you are looking at.
Battery light is a constant on. In no position with the key in does it ever go out. And as for the key positions in your previous post, when turning the key over, battery light illuminates when the key is turned the ACC, then the "SES" light comes on when key is moved to run. "
thanks for the information. just to clarify a bit more, "with the key in", the light is on, but if you remove the key, is the light still on?
Key detection is a function of the BCM.
You might have multiple problems (especially if wiring was basterdized). In terms of the dash, if and when you get access to the IPC, you can likely follow the same "power test" as shown in the video to check the response of the IPC without any connection to the bus.
One other thing... in your "short times of running", did you notice what's up with the dash and in particular, whether there is a theft indicator lit? related to this, you can potentially overcome some of this, perhaps, by also jumping power directly to the fuel pump so that it can't be disabled IF that is the case. IF the vehicle runs in this mode, then you have narrowed down what you are looking at.
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@budwich - I'll take you through the key cycle:
Key in with cylinder in lock position: Dark
Key in with cylinder in accessory position: PRNDL & Battery light come on.
Key in with cylinder in run position: Service Engine Soon light joins the PRNDL & Battery light.
Key in with cylinder cranking: All 3 lights remain on.
If you move the key back one position at a time, the SES light goes dark when key goes from run to accessory. Then moving back from accessory to lock position, the PRNDL & Battery lights go out.
Key in with cylinder in lock position: Dark
Key in with cylinder in accessory position: PRNDL & Battery light come on.
Key in with cylinder in run position: Service Engine Soon light joins the PRNDL & Battery light.
Key in with cylinder cranking: All 3 lights remain on.
If you move the key back one position at a time, the SES light goes dark when key goes from run to accessory. Then moving back from accessory to lock position, the PRNDL & Battery lights go out.
Forgot to mention...
When your DATABUS Diagram is oriented horizontally... way down on the Lower Left Side, it shows where Pin 4 & Pin 5 exit the DLC and end up as Grounds G102 & G201. If you look at @MAY03LT 's Video... that particular Common Class 2 Network Grounds at G201 and SP201 can also cause a lot of problems if it is not secured to the metal body of the SUV
(Please note that Drew frequently uses "Blue Language" that is not appropriate for "Tender Ears" if your kids are hovering around the Computer):
When your DATABUS Diagram is oriented horizontally... way down on the Lower Left Side, it shows where Pin 4 & Pin 5 exit the DLC and end up as Grounds G102 & G201. If you look at @MAY03LT 's Video... that particular Common Class 2 Network Grounds at G201 and SP201 can also cause a lot of problems if it is not secured to the metal body of the SUV
(Please note that Drew frequently uses "Blue Language" that is not appropriate for "Tender Ears" if your kids are hovering around the Computer):
Mooseman
Moderator
They all have an immobilizer. It's possible that some export models use a separate VATS module (with PassKey 3 like in the Saab with chipped keys) and all others have PassLock (like in TB's without chipped keys) that just uses the BCM for the security.
For how the IPC works, there are two or more separate power inputs. One is constant B+ and the other(s) is switched. When put on ACC, it is normal for the BAT light and PRNDL to come on and nothing else. How these are activated is unknown but it's possible if it gets a signal over the CANBUS that a module is on via the ACC that it will light them while using power from the B+ to power them. And when put to RUN, then it goes into bulb check and everything should be on and ready for input from the PCM.
For how the IPC works, there are two or more separate power inputs. One is constant B+ and the other(s) is switched. When put on ACC, it is normal for the BAT light and PRNDL to come on and nothing else. How these are activated is unknown but it's possible if it gets a signal over the CANBUS that a module is on via the ACC that it will light them while using power from the B+ to power them. And when put to RUN, then it goes into bulb check and everything should be on and ready for input from the PCM.
Thanks for the suggestion @MRRSM - that was one of the first things I checked. Connector is fastened securely.
I was talking with my buddy who's the sure tech and he's been taking to his master tech mechanic about this too, here's his reply to the defective instrument panel, CANBUS, module issue:
"I talked to him and he said that all those modules have to send a signal to the pcm and the pcm sets the dash lights. I truly believe that if the instrument panel was defective you wouldnt have a no start condition. I've never heard of anything like that happening. Plus if there was a problem with the canbus you wouldnt be able to pull codes because the instrument panel would shut the canbus lines down. I believe it's a pcm."
I was talking with my buddy who's the sure tech and he's been taking to his master tech mechanic about this too, here's his reply to the defective instrument panel, CANBUS, module issue:
"I talked to him and he said that all those modules have to send a signal to the pcm and the pcm sets the dash lights. I truly believe that if the instrument panel was defective you wouldnt have a no start condition. I've never heard of anything like that happening. Plus if there was a problem with the canbus you wouldnt be able to pull codes because the instrument panel would shut the canbus lines down. I believe it's a pcm."