Circuit Description
The body control module (BCM) monitors and supplies an output voltage on the door unlock control circuit. When the BCM receives an unlock command from the remote control door lock receiver or the ignition key is removed after an automatic door lock function has been activated, if programmed, the BCM supplies voltage on the door unlock control circuit to unlock the passenger doors.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B3147 Passenger Doors Unlock Switch Circuit Low |
| • | DTC B3148 Passenger Doors Unlock Switch Circuit High |
Conditions for Running the DTC
B3147
| • | The system voltage must be between 9-16 volts. |
| • | The BCM supplies a voltage signal on the door unlock control circuit. |
B3148
The system voltage must be between 9-16 volts.
Conditions for Setting the DTC
B3147
| • | When the BCM supplies a voltage signal on the door unlock control circuit and the door unlock control circuit is shorted to ground. |
| • | The above conditions must be met for 250 milliseconds. |
B3148
| • | When the door unlock control circuit is shorted to battery voltage. |
| • | The above conditions must be met for 904 seconds. |
Action Taken When the DTC Sets
| • | The door lock system will not UNLOCK the passenger doors from the keyless entry transmitter. |
| • | The door lock switches will not UNLOCK the doors. |
| • | The automatic door locks will not operate. |
Conditions for Clearing the DTC
| • | A current DTC will clear after the next fault free ignition cycle. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
Diagnostic Aids
| • | Perform a visual check for loose or poor connections at all related components. |
| • | A short to battery voltage in the door unlock control circuit could be cause by a faulty door lock switch. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the door unlock relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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This step verifies that the BCM is providing voltage to the door unlock relay.
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This step tests for an open in the ground circuit to the door unlock relay.
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This step tests if voltage is constantly being applied to the door unlock relay.
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After replacement of the BCM, you must calibrate the new module for proper operation.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Door Lock/Indicator Schematics | ||||
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 door unlock relay turn ON and OFF with each command? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 4 | Go to Step 5 | |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 8 | Go to Step 10 | |
Does the test lamp remain illuminated with each command? | -- | Go to Step 7 | Go to Step 6 | |
6 | Test the door unlock control circuit of the door unlock relay 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 13 | Go to Step 9 |
7 | Test the door unlock control circuit of the door unlock relay 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 13 | Go to Step 9 |
8 | Inspect for poor connections at the door unlock relay . 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 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of 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 13 | Go to Step 12 |
10 | Repair the ground circuit of the door unlock relay . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 13 | -- |
11 | Replace the door unlock relay . Did you complete the replacement? | -- | Go to Step 13 | -- |
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 13 | -- | |
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
