• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
12 Volt Reference | B2945, B2955 | B2945, B2955 | B2945, B2955 | - |
Security System Sensor Signal | B2955 | B2955 | B2955 | B2960 |
Security System Sensor Low Reference | - | B2955 | B2955 | - |
The Passlock immobilizer 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 a 12 volt reference and low reference for the Passlock sensor. The BCM also measures the security system sensor voltage via the signal circuit.
When the ignition cylinder is rotated with a proper mechanically cut key, a magnet on the cylinder passes near the Passlock sensor within the ignition lock cylinder case. The magnet activates the security hall effect 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 a valid range, the BCM will send a fuel enable serial data message to the engine control module/powertrain control module (ECM/PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a fuel disable serial data message will be sent to the ECM/PCM to disable starting of the vehicle.
Ignition is in the ACCY or RUN position
Voltage seen by the TDM at the security system sensor supply voltage circuit is greater or less than the expected value.
Voltage seen by the TDM at the security system sensor signal circuit is not within the specified range.
Voltage seen by the TDM at the security system sensor signal circuit is within the specified range, but not the learned value.
The TDM has determined a tamper condition exists within the Passlock sensor.
• | Vehicle starting will be disabled. |
• | The security indicator will be illuminated. |
• | A current DTC will be cleared when the TDM detects the fault is no longer present |
• | A history DTC will be cleared after 100 malfunction-free ignition cycles. |
Immobilizer Description and Operation
Control Module References for scan tool information
⇒ | If any items are near the Passlock sensor which may create a magnetic field, remove them. |
⇒ | If greater than the specified range test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If greater than the specified range, test the 12-volt reference circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
⇒ | If not within the specified range, test the 12-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
⇒ | If less than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the BCM. |
⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. |
⇒ | If not within the specified range or the value does not remain steady, replace the Passlock sensor. |
⇒ | If the BCM does not learn the data voltage or the vehicle does not start, replace the BCM. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for BCM replacement, setup, and programming |