B2957

CIRCUIT DESCRIPTION
The Passlock system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. The Body Control Module (BCM) provides security system sensor power and low reference for the Passlock sensor. The BCM also measures the security system sensor voltage.

When the correct key is used to start the vehicle, a magnet on the lock cylinder passes close to the Passlock sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the Passlock sensor which completes a circuit from the security sensor signal circuit through a resistor to the security sensor low reference circuit. The resistance value will vary from vehicle to vehicle. The BCM will measure the voltage on the security sensor signal circuit and compare this voltage to a previously learned voltage. If the voltage measured is within the valid range, the BCM will send a class 2 message to the Powertrain Control Module (PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a class 2 message will be sent to the PCM to disable starting of the vehicle.

CONDITIONS FOR SETTING THE DTC
^ The ignition switch is ON.
^ The BCM signal input is less than 0.4 volts for 1 second after turning the ignition switch to the CRANK position.

ACTION TAKEN WHEN THE DTC SETS
^ The vehicle will not start if the fault occurs before you start the vehicle. The security indicator will flash for 10 minutes then turn ON steady.
^ If the vehicle is running when the fault occurs, the BCM will be in the fail enable mode allowing the vehicle to start and run. The security indicator will be ON.

CONDITIONS FOR CLEARING THE DTC
^ The DTC will clear once the ignition cycle has occurred without the fault recurring.
^ The BCM history codes will clear once 100 concurrent ignition cycles occur without the fault recurring.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ Use a scan tool in order to inspect the Passlock data voltage and the Passlock code.
^ Inspect the Passlock sensor harness for an intermittent or a short to ground. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.
^ Following a repair the tamper timer needs 10 minutes in order to expire.

TEST DESCRIPTION

Steps 1-10:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for proper operation of the circuit in the high voltage range.
4. Tests for a short to ground in the Passlock sensor signal circuit.