Circuit 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, then 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 subsystems status and acute subsystem failures.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2957 Security System Sensor Data Circuit Low
Conditions for Setting the DTC
| • | The ignition switch is ON. |
| • | The body control module (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 Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | Following a repair the tamper timer needs 10 minutes in order to expire. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for proper operation of the 5-volt reference circuit from the BCM.
-
This step checks for a voltage drop through the Passlock resistor located in the ignition switch. Voltage in this step will vary due to unique differences in each individual Passlock resistor.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Is the 5 V reference circuit signal circuit voltage approximately equal to the specified value? | 5 V | Go to Step 3 | Go to Step 4 | |
Important: Do not start the vehicle. Is voltage measured at the off/run/crank voltage circuit? | -- | Go to Step 6 | Go to Step 5 | |
4 | Inspect the 5 V reference circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 6 |
5 | Inspect the Off/Run/Crank voltage circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 |
6 | Inspect for poor connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
7 | Inspect for poor connections at the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 |
8 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
9 | Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 | Perform the Programming Theft Deterrent System Components procedure. Is the repair complete? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
