NEED HELP Security issue/no start

I have a 2008 Trailblazer with a 4.2 and I've had lots of problems with it but recently I changed the fuel pump and I had to pick the lock to get into the vehicle but after that the security light came on I will not allow the door locks or Windows or anything to work and it will not start it used to start but then die but now the security light stays on and will not even start up at all just turn over also the.. we replaced the lock cylinder in the ignition but still cannot get nothing when we turn it I have to jump the starter relay to get it to turn over but still will not start.. please help
 

aaserv

Well-Known Member
Did you use the search function to ck the previous posts??? I dont know much about the security system and unfortunately there is not many members online this evening. But I know Ive seen lots of posts on the forum about it, quite possibly you may find an answer in 1 of them.
Regardless when the posse gets here they'll help you resolve it so don't go throwing parts at it yet.....
 

coolasice

Well-Known Member
I have a 2008 Trailblazer with a 4.2 and I've had lots of problems with it but recently I changed the fuel pump and I had to pick the lock to get into the vehicle but after that the security light came on I will not allow the door locks or Windows or anything to work and it will not start it used to start but then die but now the security light stays on and will not even start up at all just turn over also the.. we replaced the lock cylinder in the ignition but still cannot get nothing when we turn it I have to jump the starter relay to get it to turn over but still will not start.. please help
Hmm.. start from the beginning... what caused you to change the fuel pump? what sort of problems did you have prior to the pump? did all the security problems start after changing the pump or before?
 

MRRSM

Lifetime VIP Supporter
Some possible areas to investigate:

(1) Misaligned Ignition Switch Plastic-Nylon Teeth match up to the New Metal Key Tumbler.
(2) Failed BCM Unit under the Rear Driver's Side Passenger Seat at the Fuse Box.
(3) Shorted or inoperative Lift Gate Module (with possible Shorted Wires in the Gate to Body Conduit) ***

*** This Video does a good job of showing the Liftgate Module IN PLACE and ALL Wiring on the Gate Door Interior as well as the Conduit thru-access to the upper body where the Wires can work-harden and break apart as an EXCELLENT reference to a possible cause for Failed Key Fobs... if this issue is also involved.

 
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Mooseman

Moderator
Moved and changed the title.

Ignition switch is a usual suspect for electrical issues. It is a fairly cheap part and easy to replace. Use ACDelco only as others are not as reliable.

Another possibility is it may need a security relearn. Try the procedure as described in this thread:
PCM Security Relearn

As a hail Mary, you could disconnect the battery for 30+ minutes to reset the works.

Beyond that, I think you would need a high end scanner (i.e. Tech 2 or Solus) to track down the issue. It is possible that the BCM or VATS modules may be the issue however, any replacement would need to be programmed to your truck.
 
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Josh2008tb

Member
When first bought it sometimes it would stall..noticed previous owner ran his own ground to the body for fulepump.. doing research from this website and I figured out that the fuel pump relay was overheating and would shut off so I ran my own relay to the fusible link and ran a toggle switch for the fuel pump and it worked fine for a couple months then one day just wouldn't start... didn't think I could even hear the fuel pump so I replace the fuel pump, all the wires for the fuel pump have been cut previously so I had to rewire it.. figured out that the fuel pump was not bad after all and I got it to start but would shut off immediately with the passlock 2.. I will add in there that I had to pick the driver side door to get in the vehicle after the battery died I changed the ignition switch I put a new ignition lock cylinder and keys. Now the vehicle will not even start and the security comes on but remains constant, no flashing. No crank no start. Will only turn over if i jump the starter relay but still no start.
 
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Josh2008tb

Member
Did you use the search function to ck the previous posts??? I dont know much about the security system and unfortunately there is not many members online this evening. But I know Ive seen lots of posts on the forum about it, quite possibly you may find an answer in 1 of them.
Regardless when the posse gets here they'll help you resolve it so don't go throwing parts at it yet.....
Ya iv replaced underhood fuse box fule pump, ignition switch, ignition lock cylender, rack and penion, powerstering pump and starter in last 8 monthes...im tired...bit now i know so much about these trailblazers that im gonna stick with them...
 
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Josh2008tb

Member
Some possible areas to investigate:

(1) Misaligned Ignition Switch Plastic-Nylon Teeth match up to the New Metal Key Tumbler.
(2) Failed BCM Unit under the Rear Driver's Side Passenger Seat at the Fuse Box.
(3) Shorted or inoperative Lift Gate Module (with possible Shorted Wires in the Gate to Body Conduit) ***

*** This Video does a good job of showing the Liftgate Module IN PLACE and ALL Wiring on the Gate Door Interior as well as the Conduit thru-access to the upper body where the Wires can work-harden and break apart as an EXCELLENT reference to a possible cause for Failed Key Fobs... if this issue is also involved.

I have
Some possible areas to investigate:

(1) Misaligned Ignition Switch Plastic-Nylon Teeth match up to the New Metal Key Tumbler.
(2) Failed BCM Unit under the Rear Driver's Side Passenger Seat at the Fuse Box.
(3) Shorted or inoperative Lift Gate Module (with possible Shorted Wires in the Gate to Body Conduit) ***

*** This Video does a good job of showing the Liftgate Module IN PLACE and ALL Wiring on the Gate Door Interior as well as the Conduit thru-access to the upper body where the Wires can work-harden and break apart as an EXCELLENT reference to a possible cause for Failed Key Fobs... if this issue is also involved.

I replaced the ignition switch and tried multiple Keith positions and I'm sure I got the right setting for it..how can i test the liftgate modual? Key fab dont work and the ignition wont even turn it over have to jump starter relay..i have a pcm and bcm from another 2008 but i will have to get it programed to see if its that...hopfully theres a way to check the liftgate modual...
 

MRRSM

Lifetime VIP Supporter
Some more suggestions:

Visit this Link and Download a GM OEM Shop Manual (courtesy @Mooseman) :


(1) Using a DMM or a DVOM... Test the Static Battery Voltage and note the measurement in your next Post. The Modern GM PCM-ECM Powering demands can be VERY Touchy and having a Reliable Battery as Fully Charged as possible is a good place to start... Sorry for not mentioning this first.

(2) "...all the wires for the fuel pump have been cut previously so I had to rewire it.."

There is No Doubt About It... Your Next Best Move is to get a Lighted "Scope on a Rope" and Check the Wiring FROM THE FUSE BOX in the Power Distribution Center leading TO the FUEL PUMP for Continuity... Both in KEY OFF... KEY ON and doing so while performing Before and After checks on ALL Fuses involved to see if any Fuses Burn Out when the Key On "Start/Run" occurs, short of actually starting the Engine. Obviously, any wiring involved that gets "HOT in RUN" vs. "HOT AT ALL TIMES" should be identified and checked for any Shorts to Ground.

If your chosen method of Wire Repair involved the Technique of using "Twisted Wires, Acorn Insulator Nuts and Electrician's Tape..." The involved Cut or Damaged Wires should be pre-sleeved with Auto Quality Heat Shrink Tubes and then directly Soldered together and heat Shrink Sealed. This procedure should NOT be done if there are Gasoline Fumes or Fuel Leaks in the immediate vicinity to avoid Fire or an Explosive Ignition and Flame from this technique.

(3) Review Post #5 for @Mooseman 's suggestion about clicking on the link to the Security Re-Learn Thread and see if the vehicle Starts after you follow those directions to the letter.

(4) You are not there yet... but you should be able to use a Used PCM to get the SUV to Start and Run if the one in there now is FUBAR. IIANM... perhaps the same idea with the BCM ...which MAY still need to be programmed via a Tech 2 and SPS to ensure that the Vehicle VIN and Security set up matches the one in the OEM installed BCM.

NOTE:

I Do NOT think that THIS is where the present problem lies... but to Answer your Question about the Lift Gate Module and to help you to understand more about it ...please read on.

(5) The Question of "Testing" an LGM (Lift Gate Module) is simply a Binary Problem:

a. Does the Vehicle Start-Run with the LGM CONNECTED to the Class 2 Network?
b. Does the Vehicle Start-Run with the LGM DIS-CONNECTED from the Class 2 Network?


With the GM Class 2 Databus Design operating between 0-7 Volts DC operating on a Single Wire, it means that ALL of the Modules share ONE SINGLE COMMUNICATION Strand. This design is arranged to allow ALL of the Modules on the Network to meet up at only Two Common Communication Junction "Combs". These are called "Splice Packs" in the GM Service Manual.

One Comb is under the Driver's Side dashboard and the Other Comb is under the Carpet Flap beneath the Passenger Side rear Seat. ANY Single Malfunctioning Module is capable of Disabling the Entire Class 2 Network if either Shorted to Ground... or Shorted to Power at 12 Volts DC.

In this way , the LGM CAN be Taken Off Line as a functioning, connected Module WITHOUT having to tear apart the Rear Lift Gate to yank out the Three Connectors to do so. Please note that with the LGM Dis-Connected, the Remote Key Fob Entry will NOT Function... but trying this out MAY allow you to use the Ignition Key to Start the SUV and go on from there.

(6) Use a Higher End OBD2 Scanner capable of recognizing and reporting UXXXX Codes (Class 2 Network Communications Error Codes) for any Communications problems.

(7) Next, you can locate these two GM Databus Ribbed Steel Network Junction "Combs":

a. Under the Left Side of the Driver's Side Dashboard.
b. Under a Carpet Flap beneath the Passenger Side Rear Seat. (The LGM is on THIS One).

To help you see this entire Diagnostic Process at play with the correct tools to do so... Please Watch (Entirely) this long... but excellent Video from Robinson Auto showing how this process works:

 
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Josh2008tb

Member
Everything checks out with the ignition switch wires..i have a spare pcm and bcm and still does the same....does any one know if a 08 tranny eill work in 04 or 05 tb 4.2
 

Mooseman

Moderator
Everything checks out with the ignition switch wires..i have a spare pcm and bcm and still does the same
Of course it would be the same as the BCM has to be programmed to the truck's key cylinder. Without a Tech 2 or high end scanner to reprogram it, this won't work.

Have you tried the other suggestions?

does any one know if a 08 tranny eill work in 04 or 05 tb 4.2
Please don't mix issues as this is not related to the security issue. You already started another thread about this.
 
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Josh2008tb

Member
Of course it would be the same as the BCM has to be programmed to the truck's key cylinder. Without a Tech 2 or high end scanner to reprogram it, this won't work.

Have you tried the other suggestions?



Please don't mix issues as this is not related to the security issue. You already started another thread about this.
Ok so everything seems to have correct voltage and is hot when it needs to be...i probed the lol yellow wire with black stripe and grounded the testlight and when in the crank position the SUV will turn over but if i don't probe it then the starter dont turn over..i can jump the starter relay and it will turn over but won't start..it will start with starting fluid so i know it's getting spark....If the SUV is in theft mode do i have to have it reset from dealership?...what am I missing? Also how do i test the neutral safety switch to see if its good?..
 

Mooseman

Moderator
Have you tried all the suggestions in post #5, especially the security relearn? I think beyond that, it would be dealer time. The neutral safety switch would not activate the security light.
 

budwich

Well-Known Member
the neutral switch appears to be function as your "test light jump" works to turn the starter. This would not happen if the switch was bad / broken. Your "testlight test" proves your basic starter circuitry is good. Your problem is that your fueling is not happening as you need to inject starter fluid (in addition to the "jumpering" to cause a run.
What happens IF you jumper to cause a start AND provide "jumpered" battery and ground to the pump, does the truck stay running (assuming once it starts)?

Since you "broke" into your truck, it is likely that you triggers the anti theft / disable circuitry. Post a picture of your instrument panel with the key turned to "ON".
 
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Josh2008tb

Member
Have you tried all the suggestions in post #5, especially the security relearn? I think beyond that, it would be dealer time. The neutral safety switch would not activate the security light.
and never shuts off so I can't do the relearn process unless there's another way around it and you can help me
 

Mooseman

Moderator
If after 10 minutes as per the security relearn, if the security light doesn't go off, there's an issue with the VATS. Dealer time.
 

MRRSM

Lifetime VIP Supporter
Yes... as per our Members @limequat and @Kelly@PCMofNC ... The VATS option can be deleted using HP-Tuners via loading, modifying and then re-installing the PCM Calibration(s). Saving the OEM version right off the bat is Best Practices and then renaming the modified flavor prior to writing the New Calibration back to the PCM. Also Speed-Tuning Shops can do this... for a Price... assuming they are familiar with the unique P-10 PCM used in the GMT-360s.
 
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Mooseman

Moderator
Caveat: The security light will still flash in your face while driving (My tuned Saab does this). Easy enough to fix with tape or rip off the LED in the cluster for it. The truck will still start and drive though.

Edit: lime-swap.com (@limequat ) is cheaper than PCM of NC and is basically the same service.
 

Up And Down

Well-Known Member
The VATS system is beyond my knowledge of this truck. What I am wondering though, is if there is any type of electrical connector attached to the driver door lock cylinder or latch mechanism? The reason I ask is because you said twice that this isssue started when you picked the lock. For the problem to be related there would have to be an electrical connection that was damaged that is telling the PCM not to let the truck start. There has to be something there because if you lose your fob you can still open the truck and disarm the security system with the key.
 

Mooseman

Moderator
There is a switch or sensor in the door latch that lets the BCM know if the door was opened with the key or not (i.e. with the lever inside). This is mostly for the content theft alarm, if equipped, and activating the interior lights. It will not interfere with VATS. In fact, if the content theft alarm is activated, it is stopped using the key in the ignition or the key fob.
 
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Josh2008tb

Member
So here is an update I had the fuel pump hooked up wrong now it is pumping fuel but will start and shut right off with the security security light stays on trying to do the relearn process but it's not working is it dealership time or is it junkyard or sale also does anyone know if a weight in 09 absolutely have to be reset from dealership?
 

Mooseman

Moderator
I'm afraid so but there is another option. You could send your PCM to get tuned to ignore the VATS and start regardless of the security state. @limequat at lime-swap.com can do this for $99, shipping back to you included. And he can also do a few improvements at the same time. The only problem left would be the security light flashing constantly but that can be taken care of with some tape or ripping the LED out of the cluster for it.

Question about having PCM tuned
 

Mooseman

Moderator
check the voltage conditions at the BCM.
Good idea. An indication of a BCM issue is other stuff not working like gauges, lights, windows, locks, etc.
 

Mooseman

Moderator

Mooseman

Moderator
Are you talking about a PCM security relearn or a BCM/VATS reprogramming? Two different things here.

Did you go to the link?
 
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Josh2008tb

Member
Yes and it said "that I can use a spare PCM from any vehicle of that year trailblazer and I should be able to get it to work with the security relearn is that possible I also threw the other PCM in one time just to see if it will work do you think I ruined that PCM now by putting that one in there or is it still possible that I can get it to do the relearn I got it off of 08 trailblazer from the junkyard
 

Mooseman

Moderator
It should work with the relearn in the link. You won't ruin a PCM by just connecting it.
 
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Josh2008tb

Member
Awesome MOOSEMAN...U BEEN A BIG HELP... I'M GOING TO GO TRY IT NOW.. ALSO WE CHANGE THE LOCK CYLINDER WITH THE NEW ONE SO IT HAS A DIFFERENT KEY FOR THE IGNITION AS THE DOOR LOCKS WILL THAT BE AN ISSUE
 

Mooseman

Moderator
It shouldn't unless you disturbed the VATS sensor in the steering column. Replacing the key cylinder shouldn't trigger VATS.
 
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Josh2008tb

Member
I disconnected the battery and swaped PCM with spare..tried the relearn but security light wouldn't go off after the 11 min...is it suppose to?.. I'm stumped..also was gonna try the resister on the wires to bipass the vats but not sure exactly how..would disconnecting the Denver on the ignition set off the vats?
 

MRRSM

Lifetime VIP Supporter
Did you put the ORIGINAL BCM back in place ...prior to performing the PCM Swap? If not... Give that Combo a try.
 
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Josh2008tb

Member
I did not swap the bcm only the PCM..I do have the bcm off the other tb as well..is there any way you can call me? I know I'm getting heavy on the questions but it would be easier for me to explane.. I'm in Iowa..I can give you my number
 

Mooseman

Moderator
If the light isn't going out, it's likely the VATS has been tripped or lost its programming. If the BCM seems to be responding with other stuff working correctly, to avoid a trip to the dealer and the expense, I'd send it to get tuned and have VATS turned off. You'll have the light flashing, which you can tape over or rip out the LED in the cluster.

Every once in a while, we get someone with a VATS failure. Most of the time, it's on a desolate road at night with no cell service. Even if you fix it properly now, it can happen again.
 

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