EagleTribune.com, North Andover, MA


December 30, 2012

Antitheft system causes trouble

I own a 1998 Pontiac Grand Am SE. She has 242,000 miles on her. Recently the theft light comes on, blinks and then stays on. Sometimes the car will die starting up, then it may start up and run fine. Sometimes the light will stay on, and other times the light will go out.

I was told that this was a safety feature GM installed, although a cheap one, to prevent stolen vehicles. I was wondering if this is something I can fix or disable myself. I have an aftermarket alarm system that has been installed on this vehicle since 2000. That has keyless entry, which I use regularly.

I was told by one person that buying a new battery for my clicker would solve the problem. Another person told me I have a bad fuse that needs to be replaced, and another said I could disable the system by cutting a yellow wire running from my ignition switch. Can you help me? I depend on my vehicle for my job and drive some distance every day. What can I do?

Your Grand Am employs GM’s Passlock antitheft system, which is known for causing intermittent starting headaches and big repair bills to fix it. A sensor in the steering column determines the ignition lock cylinder has successfully rotated, which requires the correct key. This creates an electrical output to the antitheft brains in the instrument panel cluster, which then sends an “OK” handshake to the powertrain control module. That allows normal function of the fuel injectors. Should an ignition switch input occur without the accompanying sensor signal — perhaps if a hammer, pliers, and screwdriver are used to rotate the lock cylinder — no IPC/PCM handshake occurs. The fuel injectors are cut off, causing the engine to start then stall, and the theft deterrent light is illuminated.

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