Fixing my GM Passlock Problem Once and For All (2004 Chevrolet Impala)

Fixing my GM Passlock Problem Once and For All (2004 Chevrolet Impala)
The PassLock system was designed to prevent vehicle theft by disabling fuel to the engine if attempts are made to start the vehicle without the correct bitted key. PASSLock increased the level of security while retaining the ease of service and costs offered by standard ignition lock systems. Unlike the General Motors PASSKey I/II, VATS, PASSKey III, or keyless, the security of the PassLock system is built into the lock and is not dependent on a specialized key or separate device.
No programming is required for the PASSLock-equipped vehicle to accept additional keys. Any key blank with the proper profile cut to the correct depths can be used to operate the ignition lock.
For the 1995-1/2 model year, General Motors introduced PASSLock, the first ignition lock equipped with a magnet mounted into the ignition lock cylinder and a corresponding Hall-effect sensor mounted into the housing assembly. When the correctly cut key is inserted into the lock cylinder and rotated, the magnet registers on the sensor’s three switch points. The sensor electronically signals the vehicle’s on-board computer, and the fuel supply remains on if the electronic value matches the code stored in the computer.
If the values do not match, the fuel supply is shut off. After three consecutive failed attempts, PASSLock will enter Long Tamper Mode, disabling the engine for 10 minutes while the Theft System indicator on the instrument panel flashes.
The PASSLock system is designed such that forced rotation normally damages the electronics, immobilizing the vehicle. According to General Motors, should the ignition lock be force rotated, the lock must be replaced in order to operate the vehicle.

Note: The theft deterrent function of the PASSLock System locks out the fuel injectors after the engine is started. However, before a tamper mode engages, the car may run for a few seconds. The engine will then stall.

Depending upon the year and the model, replacing the ignition lock can result in the need to disassemble the dashboard. Early vehicles equipped with the modular PASSLock ignition locks had a long wire that went from the ignition switch to a connector behind the instrument panel. The modular in-dash ignition locks and the CSS ignition lock cylinders do not have wiring that must be plugged in.

When replacing a PASSLock ignition lock, there is a one in 10 chance the Hall effect sensor is the same value as the lock being replaced. Replacement locks do not have an identified sensor value. When the starter is engaged for the first time and the engine starts but stalls, the instrument panel security light will flash, indicating the vehicle is in the secure mode (it will not start) and must be programmed to accept the new lock.

Note: To avoid programming when the ignition lock needs to be replaced, use the housing of the ignition lock, which contains the Hall-effect switch. Replace only the plug. The Hall-effect switch determines the magnetic value.
To reprogram PASSLock I ignition lock:

Step 1. After replacing the lock, try to start the vehicle with a correctly cut key. There is a one in 10 chance that the car will start.

Step 2. If the new lock does not match the electronic value in the vehicle’s computer, an indicator light on the instrument panel will begin flashing and the car will be disabled.

Step 3. Leave ignition in the ON or RUN position.

Step 4. After approximately 10 minutes, the light will stop flashing and remain ON. The onboard computer has then been programmed to accept the new lock’s signal. The car can be started.

If the indicator light turns off, the vehicle is probably equipped with a PASSLock II system. Continue with the following programming procedure.



Occasionally, a PASSLock-equipped vehicle will have problems starting. The following information can help to determine the cause of the problem.

The PASSLock system does not disable the starter; it only disables the fuel after the engine has started. If the vehicle will not crank, PASSLock cannot cause this condition. If the vehicle starts, but stalls quickly, this condition can possibly be related to PASSLock.

Most PASSLock-equipped vehicles have a telltale indicator in the instrument panel. When a PASSLock-equipped vehicle is being started, the instrument panel warning light for PASSLock remains on until the engine starts. For this reason a “No Start” condition should not be confused with PASSLock System fault.