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 B2947 Security System Sensor Power Circuit Low
Conditions for Setting the DTC
The BCM detects a short to ground on the Passlock sensor power circuit for one second, with the ignition switch in the ACCESSORY, ON, or START position.
Action Taken When the DTC Sets
| • | The BCM stores DTC B2947 in memory. |
| • | The BCM sends a message to the instrument cluster to turn the SECURITY indicator ON. |
| • | In addition, the BCM will take 1 of 2 actions: |
| - | If the Passlock sensor power circuit is shorted to ground when attempting to start the engine, the BCM will NOT send a message to the PCM to enable fuel delivery to the engine. The vehicle will exhibit an engine no start or starts then stalls condition. |
| - | If the Passlock sensor power circuit is shorted to ground after the engine has started, the BCM enters a fail-enable mode. Upon subsequent engine start attempts, the BCM will send a password message to the PCM via the class 2 serial data link to enable fuel delivery to the engine. The engine will start. |
Conditions for Clearing the DTC
| • | The BCM no longer detects a short to ground in the Passlock sensor power circuit. |
| • | When a short to ground 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 between the Passlock sensor power circuit and the Passlock sensor ground circuit, or a short to ground on the Passlock sensor power circuit.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies that DTC B2947 is a current DTC.
-
Tests for a short to ground in the Passlock sensor or the pigtail harness.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Theft Deterrent System Schematics Connector End View Reference: Theft Deterrent System Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool display B2947 as a current DTC? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | |
Does the voltage measure approximately battery voltage? | Go to Step 6 | Go to Step 4 | |
4 | Test the Passlock battery voltage circuit for a short to ground. 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 7 |
6 | Inspect for poor connections at the Passlock sensor. 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 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 and Start Switch Replacement in Instrument Panel, Gages, and Console. 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 procedure? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 3 | System OK |
