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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2948 Security System Sensor Power Circuit High
Conditions for Running the DTC
The ignition switch is cycled to CRANK, released to ON and then cycled to OFF.
Conditions for Setting the DTC
| • | The BCM turns the Passlock™ sensor power OFF after the ignition switch is turned OFF. |
| • | If the BCM still senses battery voltage for one second after the shut down of voltage, this DTC will set. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2948 in memory. |
| • | The vehicle will start and run. |
| • | The SECURITY indicator remains illuminated. |
Conditions for Clearing the DTC
| • | The BCM no longer detects a short to battery in the Passlock™ sensor power circuit. |
| • | When a short to battery is no longer present on the Passlock™ sensor power circuit, the ignition switch must be cycled from OFF to ON before this DTC can change from a current DTC to a history DTC. |
| • | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
Inspect for a short battery on the Passlock™ sensor power circuit with the ignition switch OFF.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Theft Deterrent System Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the scan tool display DTC B2948 as a current DTC? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
|
Important: The use of a DMM is crucial in this step because voltage may be measured for 10 milliseconds.
Does the voltage measure near 0 volts? | Go to Step 7 | Go to Step 4 | |
4 | Test the Passlock™ battery voltage circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 5 |
5 | Inspect for poor connections at the body control module (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 10 | Go to Step 6 |
6 | Inspect for poor connections at the Passlock™ sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
7 | 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 10 | -- |
8 | Replace the Passlock™ sensor. Refer to Ignition Lock Cylinder Case Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 9 | -- |
9 | Perform the Passlock™ learn procedure. Refer to Programming Theft Deterrent System Components . Did you complete the repair? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 3 | System OK |
