Gm theft deterrent

Max Technician California Posted   Latest   Edited  
1997 Chevrolet Cavalier 2.2L (4) 3-spd (THM125C)
Crank / No Start

1997 cavalier customer complains intermittently crank wont start she leaves the keep on 10 minutes and now the engine starts. has code p1601, p1629 for the theft deterrent system. We have replace the instrument cluster 3 times. 2 clusters completely stop communicating. Check connections at the cluster and voltage is good. We also replaced the pass lock sensor and the ignition electrical switch. I have not experience the problem myself. Only a couple times while cycling the ignition the theft light did not illuminate. Has anyone experience something similar to this problem?

Tim Mechanic
Tim Default

I have no experience with the Cavalier, but we have a few 97-98 vintage Chevy trucks where I work. They are pretty maddening in how intermittent they fail. I can remember that we finally replaced the BCM after changing the ignition switch and passlock sensors on two of them. The BCM was the fix. I'm sorry I don't have a good way to test them. Every single time I had them in the shop I could not…

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Matthew Owner/Technician
Matthew Default

When you replaced the passlock sensor did you use aftermarket or OE? I've had some that were not very reliable sending signals for processing. If she can leave the key on and it does the relearn/prove out then I would still be looking at the sensor part.

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Max Technician
Max Default

Oe pass lock sensor

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Brian Instructor
Brian Default

I do not recall what year this became unavailable '98 think, there was a special function available with the tech 2 that would disable the security function in the cluster. It has been at least 6 or 7 years since I have done this procedure but it will remove the passlock portion of security fro the vehicle, I do not know if the PCM still will need the clusters "approval " to start the vehicle.

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James Technician
James Default

You need to use the Tech2 to change the vehicle to Fleet Status. This will remove the security requirement.

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Jeff Technician
Jeff Default

You could remove pins from connectors for circuits involved and solder the crimps then reassemble. Also add a redundant ground to ipc ground circuit right to battery ground possible electrical noise/interference causing issue.

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Christopher Diagnostician
Christopher Default

Load test ground circuit for pass lock module and cluster. California probably doesn't see the cancer we do but issue reeks of ground problem.

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Michael Diagnostician
Michael Default

I have to look the system up, but I have bypassed chevy trucks with 2000 ohm resisters and relearned the system.

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Stuart Mobile Technician
Stuart Default

Yes Michael,the GM through the 90s and until 2001 I think, you can trick the security system like that most of the time as long as the security module is good.

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Max Technician
Max Update

This morning after sitting for 2 days the theft light came on but the engine did start. had communication to the pcm and the instrument cluster. no codes store on pcm but 2 codes on icp b1012 vtd bad signal b1014 vtd not programmed codes store. if you follow the diag tree it says to replace Instrument cluster panel.

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Raymond Owner/Technician
New York
Raymond Default

Being from the Northeast Rust Belt, the steel battery trays would rust off on the Cavaliers and cause a lot of weird things to happen. Check your ground wires to the stamped tray. The second thing is I believe if you start the car and unplug The Passlack from the ignition switch it will bypass the security system and continue to be bypassed until A. Someone plugs it back in or B. Someone unhooks…

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