B3125

DTC B3125, B3130, or B3135

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3125 00
- Left Front/Driver Door Only Unlock Circuit

DTC B3130 00
- All Door Unlock Circuit

DTC B3135 00
- All Door Lock Circuit

Diagnostic Fault Information






Circuit/System Description

The body control module (BCM), upon receipt of a lock switch lock signal, will switch the Door Lock Relay Control circuit to battery positive voltage. This will energize the LOCK relay. The remaining unlock relays receive voltage from the underhood fuse block, the BCM upon receipt of a unlock signal or driver door unlock signal will switch the appropriate unlock relay to ground. This will energize the appropriate unlock relay unlocking the appropriate doors.

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC

B3125 00

The BCM detects a fault in the driver door unlock control circuit while commanding the DRIVER UNLOCK relay.

B3130 00

The BCM detects a fault in the door unlock control circuit while commanding the UNLOCK relay.

B3135 00

The BCM detects a fault in the door lock control circuit while commanding the LOCK relay.

Action Taken When the DTC Sets

* The BCM stores the DTC to memory.
* The power door locks will not operate

Conditions for Clearing the DTC

* This DTC will change from current to history when the fault is no longer present.
* A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Circuit/System Verification

Ignition ON, command the driver door and passenger door lock actuators to LOCK and UNLOCK with the scan tool, the doors should LOCK and UNLOCK

Circuit/System Testing

1. Ignition OFF, disconnect the X1 harness connector at the I/P fuse block.
2. Connect a test lamp between control circuit terminal K4 and ground.
3. Ignition ON, command the lock rear doors ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

^ If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. Connect a test lamp between control circuit terminal K6 and B+.
5. Command the driver door unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

^ If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

6. Connect a test lamp between the control circuit terminal K5 and B+.
7. Command the unlock rear doors ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

^ If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

8. If all circuits test normal, replace the I/P fuse block.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Instrument Panel Electrical Center or Junction Block Replacement - Right Side (Impala)