For 1990-2009 cars

### Diagnostic Instructions

• | 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.

### DTC Descriptor

DTC B2957: Security System Sensor Data Circuit Low

### Circuit/System Description

The Passlock™ System is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate. The Passlock™ controller reads the coded Passlock™ data signal. The data consists of a voltage generated by a voltage divider network created between the Passlock™ assembly and the Passlock™ controller. If the data is correct, indicating rotation of the lock cylinder with the proper mechanically cut key, the Passlock™ controller sends a password to the powertrain controller via serial data to indicate that engine starting should be allowed. The Passlock™ controller also interfaces with the driver displays subsystem to indicate, via the security indicator, the Passlock™ subsystem status and acute subsystem failures.

### Conditions for Running the DTC

The vehicle theft deterrent system is in the learn mode.

### Conditions for Setting the DTC

• | The ignition switch is ON.

• | The body control module (BCM) signal input is less than 0.4 volt for 1 second.

### Action Taken When the DTC Sets

• | The vehicle will not start if the fault occurs before you start the vehicle. The security indicator will be 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

• | Inspect the Passlock™ sensor harness for an intermittent or a short to ground.

• | Following a repair, the tamper timer may need 10 minutes in order to expire.

### Reference Information

#### Schematic Reference

Immobilizer Schematics

#### Connector End View Reference

Master Electrical Component List

#### Description and Operation

Immobilizer Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Testing

Important: Do not start the vehicle when momentarily placing the ignition and start switch into the CRANK position.

1. Turn OFF the ignition. Back out the ignition key resistor signal terminal from the ignition and start switch harness connector. Reconnect the ignition and start switch harness connector. Turn ON the ignition, with the engine OFF. With a DMM, measure for 5 volts at the ignition key resistor terminal. Perform the following if voltage is not present:

⇒ | Inspect the ignition key resistor signal circuit for an open or short to ground. Make the appropriate repair.

⇒ | Inspect the BCM connector. Make the appropriate repair.

⇒ | Replace the BCM. Refer to Repair Instructions.

2. Secure the ignition key resistor signal circuit terminal into the harness connector and reconnect the ignition and start switch. Disconnect the body control module (BCM) connector and back out the off/run/crank voltage circuit terminal from the BCM harness connector. Connect the harness to the BCM. Connect a DMM between the off/run/crank voltage circuit terminal and a good ground.

Important: Do not start the vehicle. Observe the voltage while momentarily placing the ignition switch in the CRANK position. Perform the following if voltage not present:

⇒ | Inspect the off/run/crank voltage circuit for an open or short to ground. Make the appropriate repair.

⇒ | Inspect the ignition and start switch connector. Make the appropriate repair.

⇒ | Replace the ignition and start switch. Refer to Repair Instructions.

3. Inspect the BCM connector. Make the appropriate repair. If a condition is not found with the connector, replace the BCM. Refer to Repair Instructions.
4. Perform the Programming Theft Deterrent System Components procedure.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ignition and Start Switch Replacement

• | Control Module References for BCM replacement, setup, and programming