No crank no start isn't it lovely

[bennieRohde]

Okay guys.... I've been at this one for a while.
So I'll start here.
2002 GMC envoy
I've checked power from damn near everything I could think of and the grounds. Ignition switch, starter relay, fuel pump .. tons of my PCM wires to the fuse box as well (I had previously pulled the fuse box out and checked for good continuity) All mostly for the ignition and PCM connection wires.

This thing began as an intermittent no start. Sometimes it would, sometimes it wouldn't. Then it just didn't start

So, turn the key to run, dash lights are on, turn to start and it all goes black, no crank no sounds, nothing. Just dark.
Pulling the door unlock relay for whatever reason also can bring all of those lights on (sometimes no lights come on the dash) , and is how I had managed to get this vehicle started before.
I thought that it may have had something to do with the security system and getting locked out but am unsure. As there was a previous issue with the doors locking automatically. But the previous owner had just pulled the relay ( I believe it's the door lock relay)

I have been driving it for a week, no issues.
Today wouldn't start when trying to leave work. I pulled my good ol door unlock relay and got all my dash lights to come on, they weren't before. Tried to start it, and they go all black, like something is grounding out or the car doesn't think it's in park.
I went and pulled the starter relay, immediately put it back in and the car started and ran. (I've also got several of these relays I've interchanged before with no change)
However it wouldn't manually shift (it's an automatic) I had to shift it or it would drive around in 3rd gear no down or upshift. The blower motor didn't work which it normally does. And my ABS and 4wd service lights was on. Never was before.
I need some help figuring out what's causing this no crank no start issue please! Thank you for reading this...

 

[bennieRohde]

Also .. I have connected it to a OBD2 and get nothing for codes.

 

[bennieRohde]

Also.. I do believe I keep hearing about a ground from splice pack type of deal, G201 I believe it was called. Had a bunch of grounds going to it. Apparently that is in the passenger side left foot side under glove box. So I'm going to also check that and make sure that it's okay.

 

[Mooseman]

Have you checked the ignition switch? It can be the source of many electrical gremlins.

Here's a thread to check:
No Crank, Like Attempting To Start In Drive

 

[bennieRohde]

I sure did. It puts out correct voltage every where it needs to and didn't seem to have any short or grounding issue it's self.

 

[bennieRohde]

I also sort of have a parts graveyard of Chevy /GMC parts so I even hooked up another switch at one point to test as well. I do not believe it's the ignition switch. This has been probably a solid month+ of tinkering

 

[bennieRohde]

Have you checked the ignition switch? It can be the source of many electrical gremlins.

Here's a thread to check:
No Crank, Like Attempting To Start In Drive

I read through a bit of that article. I have also tested most of my connections for proper power and grounds. From fuse box to PCM and. From fuse box to ignition. Couldn't find any issues. I can jump the relay and start the vehicle just fine. It doesn't stay running however because the fuel pump doesn't engage. But I can jump that too hahah. I did, seriously and got it running. So. It's not that! Haha.

 

[mrrsm]

Welcome to GMT Nation...

Take a few minutes to observe Will Robinson's CLASSIC OBD2 Network Issues (Trailblazer) Video and observe the Two Locations for the Colored Wire Splice Packs (One is fitted Under the Driver's Side Kick Panel and One is found under the Carpet Flap beneath the Rear Passenger Seat). Take the Splice Pack Plug (COMB) out of the REAR location FIRST and then see if the Vehicle Starts. If it does... This divides the SUV in 1/2 so you can concentrate your investigation on the Modules in the back section of the SUV. Follow what Will instructs you to do for the FRONT Splice pack if it becomes necessary in this same manner:

Ordinarily... the Big Three for most Automotive No Starts involve checking out Fuel, Air and Spark.

(1) FUEL - If You think your Fuel Pump is going out... Pull the Fuel Pump Relay and after loosening the Air Box to Throttle Body... get a Can of Starter Fluid and while someone else is Cranking over the Engine... LIGHTLY Spray the Starter Fluid into the Throttle Body. If the Engine Starts... concentrate on investigating a Failing Fuel Pump. Low Fuel Pump Pressure will create Excessive In Cylinder Lean Conditions if the EFIs cannot deliver an ample Atomized Mist of Fuel. Liquid Fuel *Dribbling* out of the Spigots-Spinerets of any underfed EFIs... will NOT Burn Properly inside of the Cylinders due to poor A/F Mixtures and a Low Level of Hydro-Carbons present to assist the *Spark* along.

(2) AIR - All Engines require sufficient Compression in order to Squeeze Down the Air/Fuel Mixture enough to get a Powerful enough explosion. If your Engine has Very High Mileage and the Rings are Bad Enough NOT to Seal Off the Pistons and be able to develop sufficient OOOooomph to Start the Engine... Performing a Cylinder Comparison Compression Test will reveal this as a problem. Failed Head Gaskets can likewise release the needed Squeeze too and the results will be the same. NO START. If you have an Oscilloscope... Performing a FAST, Non-Invasive Relative Compression Test at the Fuse Box is also another option.

(3) SPARK - Unfortunately, Driving any Vehicle that has had a Persistent Flashing SES Light may be caused by excessively LEAN Combustion events due to Un-Metered Air (Leaks around the Intake Manifold) getting into the Air Stream and then, Regardless of the Cause and Origin of the Lean Conditions... soon after, the Coil Over Plugs WILL have to create a HIGH (KV) Level... Enough for the Secondary Spark event to wind up Damaging and Shorting Out the Coil Over Plug(s) in due time. Any Shorted Coil will prevent the Engine from Starting and Running until it manages to COOL DOWN and function again, if at all. Finding that you have Persistent LEAN P0300 or P0301-P0306 events (if discovered) and merely changing out the involved Coil(s) will only delay with solving the problem:



Beware TOUCHING the Tops of any of the Coil Over Plugs as your Fingers can get Badly Burned. The COPS will Overheat due to the Secondary Coil creating EXCESSIVELY High Voltage (Kilo-Volts) Oscillations Rebounding BACK through the Primary Side of the Coil. Coil Over Plugs Rubber Insulation Boots can also break down and have Carbon Arcing and Tracings develop to prevent the Spark from staying inside the Upper Combustion Chamber at the Tip of the Spark Plug due to Excessive Lean Conditions. Stuck or Failed EFIs can also create these Excessively Lean Conditions. The Flow of Electrons at the Spark Plug is GREATLY aided by the presence of a proper mixture of Hydro-Carbons and Air and it is this condition that preserves the Secondary Coil KV Events from having to Climb TOO High in order to Ignite whatever Fuel/Air Mixture is in there... just BTDC (Before Top Dead Center).

 

[bennieRohde]

Hmm. Going to check out that rear splice pack tomorrow.

 

[bennieRohde]

Also thank you for the welcoming Mrrsm

 

[Mooseman]

Is the security light on or flashing after attempting to start it? Reason I'm asking is because it won't crank AND the fuel pump doesn't work.

Are other things working? Windows. radio, etc? If the BCM or the network is not working, then that could also explain it. Could also be a bad module fouling up the network. If you can, remove the comb in the splice pack and connect the PCM, BCM together only. Check the wiring schematics for which ones to jump.

 

[budwich]

You are likely looking at "corrupt data bus" problems. You are going to have find a way to monitor the bus via an OBD device / scanner. Look at some of the posts from Tjbaker57 how this can be done. Possibly related, is problems with the lift gate module. It is susceptible to causing problems because of breaks / shorts in wiring from "historical" open / close operation. You can try disconnecting it to see if that helps with the problem.

 

[TJBaker57]

If we suspect there is a dead network there are a few rudimentary tests that can be done by anyone. No tools even required. Attention to detail is critical though.

(1) Turn the key to Accessory, that's the 1st key click. Do NOT turn it to RUN, only to ACCessory. Look at the cluster. What do you see? You should see ONLY the red battery picture turned on and the PRND321 display on. If you see these on with the key only having been turned to the ACC position this tells us that messages from the BCM are getting to the cluster. Without serial data from the BCM to the IPC at this key position these display items will be dark. [This also checks the ignition switch terminal F to terminal E contacts at least at some level.]

(2) Now turn the Headlamps switch to the ON position. Using the multifunction switch (turn signal stalk) turn on the HIGH beams. Does the blue high beam indicator in the cluster turn on? If yes this is further proof of serial data passing between the BCM and the IPC.


(3) Turn the ignition key/switch to the RUN position. Now look at the PRND321 display. Is there now an indicator bar under one of the selections that was not there in ACC position (likely Park)?? If yes this is proof that PCM serial data is passing to the IPC.

(4) With the key in the RUN position does the fuel tank level gauge work? If yes this is more proof of serial data transfer from PCM to IPC.

Does the battery level gauge work? If yes this is proof of serial data transfer between the BCM and IPC.

(5) With key in ACC, open the drivers door. Do the audible warning "chimes" sound? If yes this proves serial data transfer from DDM to BCM and also BCM to either the radio or amplifier depending on equipment options.

(6) Key at RUN, open the rear glass or hatch. Does the "gate ajar" light turn on? (above the smaller gauges at the right side of cluster). If yes this proves serial data between the LGM and the IPC.

There are likely more checks but this is enough to demonstrate that at a minimum some serial data is passing. If there were a serial data bus short to either power or ground there would be no possibility of serial data message traffic.

 

[bennieRohde]

Okay . So today I went looking for that rear splice pack. Found it and several others. One of the was taped up to hold it together I guess. As in someone was already into it. But that would have been over 5 yrs ago. Unplugged them all one by one with no noticeable change. Didn't volt or continuity check any of them though. I did check the front plug. Seems the solid thick green wire is power and I only get a beep for that one when testing that goes to the farthest wire a purple one on the other end. The rest no beep. In that video it showed the function of the power wire powering each of these individually so I figured a continuity check to see is the correct choice? So yea .. only one wire beeps when done like that.

 

[bennieRohde]

If we suspect there is a dead network there are a few rudimentary tests that can be done by anyone. No tools even required. Attention to detail is critical though.

(1) Turn the key to Accessory, that's the 1st key click. Do NOT turn it to RUN, only to ACCessory. Look at the cluster. What do you see? You should see ONLY the red battery picture turned on and the PRND321 display on. If you see these on with the key only having been turned to the ACC position this tells us that messages from the BCM are getting to the cluster. Without serial data from the BCM to the IPC at this key position these display items will be dark. [This also checks the ignition switch terminal F to terminal E contacts at least at some level.]

(2) Now turn the Headlamps switch to the ON position. Using the multifunction switch (turn signal stalk) turn on the HIGH beams. Does the blue high beam indicator in the cluster turn on? If yes this is further proof of serial data passing between the BCM and the IPC.


(3) Turn the ignition key/switch to the RUN position. Now look at the PRND321 display. Is there now an indicator bar under one of the selections that was not there in ACC position (likely Park)?? If yes this is proof that PCM serial data is passing to the IPC.

(4) With the key in the RUN position does the fuel tank level gauge work? If yes this is more proof of serial data transfer from PCM to IPC.

Does the battery level gauge work? If yes this is proof of serial data transfer between the BCM and IPC.

(5) With key in ACC, open the drivers door. Do the audible warning "chimes" sound? If yes this proves serial data transfer from DDM to BCM and also BCM to either the radio or amplifier depending on equipment options.

(6) Key at RUN, open the rear glass or hatch. Does the "gate ajar" light turn on? (above the smaller gauges at the right side of cluster). If yes this proves serial data between the LGM and the IPC.

There are likely more checks but this is enough to demonstrate that at a minimum some serial data is passing. If there were a serial data bus short to either power or ground there would be no possibility of serial data message traffic.

No. In accessory nothing. Then in run all lights turn on for a second, then most go away except sometimes they change. From ABS, seatbelts, parking brake, battery, engine service and check gauges. Also no gauges half the time. Other half, the gas gauge does move. When in on position

 

[bennieRohde]

No high beam indicator light

 

[bennieRohde]

When the car does start, as I've had it before everything does function as it normally should. Except for this very last time I had it running as I explained above.

 

[bennieRohde]

I also have to push the ignition pin in when getting the key out when the vehicle has these issues. When it doesn't, I don't have to. Idk if that matters just something to note.

 

[bennieRohde]

No. In accessory nothing. Then in run all lights turn on for a second, then most go away except sometimes they change. From ABS, seatbelts, parking brake, battery, engine service and check gauges. Also no gauges half the time. Other half, the gas gauge does move. When in on position

So I had actually still had the splice pack out when confirming which lights came on and off hah. So I put that back in. And yes it has prnd321 on dash and battery light. In accessory. That's it. Turning the key over I do still have the same message lights. But also service 4wd.

And no security light. Although previously I did have that issue and had to do a security recognition thing with the key. It's one of the magnetic ones. I haven't had the security light come on at all for a while during this now.

 

[bennieRohde]

Is the security light on or flashing after attempting to start it? Reason I'm asking is because it won't crank AND the fuel pump doesn't work.

Are other things working? Windows. radio, etc? If the BCM or the network is not working, then that could also explain it. Could also be a bad module fouling up the network. If you can, remove the comb in the splice pack and connect the PCM, BCM together only. Check the wiring schematics for which ones to jump.

Almost everything else works. Hmm. I'll look at a wire diagram. Will this allow the vehicle to start? It's probably not good to drive it like that though huh? I need to get this thing on the road regardless haha. I have a good commute to work and can't keep using the ladies car

 

[bennieRohde]

I had put an OBD2 on it a few times when the issue first began. But I don't have a data link connector to attach. The obd scanner wasn't any help it didn't show me anything. An evap code. Which may clear now cause I got a gas cap, it literally didn't have one.

 

[bennieRohde]

Note. The driver door panel switches do not work. I believe the fuse was pulled. Because it was automatically locking the driver door and previous owner didn't like that. Previous owner being girlfriends mother. Who gifted me this headache after trying to fix it for her.

 

[TJBaker57]

Seems the solid thick green wire is power

No. There is NO "power" wire anywhere in the serial data circuits. Nowhere. If there was any "power" wired to it then the whole network would be stone dead.

 

[bennieRohde]

Interesting. Okay. So that explains why not much was happening. But 4 wires I believe all get a read of like .025 volts

 

[TJBaker57]

If you can, remove the comb in the splice pack and connect the PCM, BCM together only

In a 2002 4.2 this is (should be) unnecesary as there is a redundant serial data wire (circuit #710, yellow) from the PCM direct to the BCM without any splice packs.

 

[TJBaker57]

Interesting. Okay. So that explains why not much was happening. But 4 wires I believe all get a read of like .025 volts

Here is the thing... the voltage pulses on the serial data network are so fast that a normal test meter cannot read them. We are talking about a voltage pulse no longer than 0.0002 seconds long. 200 microseconds is the longest pulse there will be. And that one only happens once per message. And there are like dozens of messages per second.

 

[bennieRohde]

Would that be for testing that? Unplugging that connection and seeing if car will start? I've tried to unplug a few modules now, trying to work my way through them. And see if any changes happen.

 

[bennieRohde]

Here is the thing... the voltage pulses on the serial data network are so fast that a normal test meter cannot read them. We are talking about a voltage pulse no longer than 0.0002 seconds long. 200 microseconds is the longest pulse there will be. And that one only happens once per message. And there are like dozens of messages per second.

Right, understood.

 

[TJBaker57]

And yes it has prnd321 on dash and battery light. In accessory

This is good. This means that the BCM and cluster can talk at least when in ACCessory.

Would that be for testing that? Unplugging that connection and seeing if car will start? I've tried to unplug a few modules now, trying to work my way through them. And see if any changes happen.

If your 2002 Envoy is like my own 2002 Trailblazer it will start and run with the forward splice pack 'comb' removed. But a lot of systems will not function right. And may be too dangerous to drive like that.

 

[bennieRohde]

Also when the dash lights do work, in accessory key position it only shows the prnd321 and battery light. In run position the gas gauge does work and so does the battery. And I can see that icon you spoke of under neath park appear in run and not accessory.
Sometimes I'll lose all of my lights before I turn the car over. I solved this by removing and placing back in the door unlock and lock relays. I specifically think it's the unlock relay. And my lights on dash would come back on.
This is intermittent. And doing that for a bit and pulling the starter relay and placing back in allowed it to start. Not this time around. Few days now.

 

[bennieRohde]

This is good. This means that the BCM and cluster can talk at least when in ACCessory.




If your 2002 Envoy is like my own 2002 Trailblazer it will start and run with the forward splice pack 'comb' removed. But a lot of systems will not function right. And may be too dangerous to drive like that.

Haha I have like an hour drive to and from work so maybe not. I couldn't get it home a few days ago. It was doing this issue. And when I finally did get it messing with the relays. It wouldn't automatically shift. I had to manually shift gears. Also no blower motor. Heat was on and working but not blowing. It normally does.

 

[TJBaker57]

No high beam indicator light

No high beam indicator light WHEN? In ACCessory? In RUN?

 

[bennieRohde]

It wasn't working. But it did now. In both accessory and run. Indicator and lights both come on.

 

[bennieRohde]

I may have tried that earlier when I had that comb unplugged to be honest. It's all plugged in now though.

 

[bennieRohde]

Also still everything goes black when I try to crank it over. All lights gone. Even the auto headlights.

 

[TJBaker57]

Also when the dash lights do work, in accessory key position it only shows the prnd321 and battery light. In run position the gas gauge does work and so does the battery. And I can see that icon you spoke of under neath park appear in run and not accessory.

This behaviour is correct. In ACC there should only be the red battery image and the PRND321 with no indicator bar.

In RUN the indicator bar and the fuel, engine temp, oil pressure gauges should work. Also the check/service engine light should be on if the engine has not started.

solved this by removing and placing back in the door unlock and lock relays.

Door lock/unlock relays? these are in the rear fuseblock under the seat.

g the starter relay and placing back in allowed it to start

And this relay is under the hood.

 

[TJBaker57]

I may have tried that earlier when I had that comb unplugged to be honest. It's all plugged in now though.

This is exactly why in my post I mentioned "attention to detail is critical". The tests I posted depend on the conditions being exactly as stated.

 

[TJBaker57]

Also still everything goes black when I try to crank it over. All lights gone. Even the auto headlights.

You may have some primary ground(s) loose or dirty. there are several (maybe 4?) on the left side on the engine block. Maybe even a battery terminal loose, dirty, corroded.

 

[bennieRohde]

Yes. I have actually found several of the grounds. And cleaned them. That's one of the first things I did. I'll go back over and check them. Also checked the multi ground on the passenger side to the right of the shifter there on the wall.

 

[bennieRohde]

And yes the door unlock relay lol. It is in the back seat. And yea the ignition fuse. For whatever reason when I lose all my lights I can pull them, specifically the unlock I believe and the dash lights will come on. Sometimes for whatever reason it all goes black. Randomly and while working on it.