Diagnostic Routine C

Diagnostic Routine C

Diagnostic Overview

The Door Locks Operate Only One Way

Refer to Wiring Diagram Set 117 for schematic and connector information Electrical Diagrams.

Normal Operations and Fault Conditions

The BCM (Body Control Module) sends voltage signals to the door lock control switches through the lock and unlock input circuits. When the lock or unlock switch is pressed, the corresponding voltage signal is routed to ground, signaling the BCM (Body Control Module) to lock or unlock the doors. The door lock control switches have a dedicated ground circuit. The BCM (Body Control Module) sends the lock or unlock request from the door lock control switch to the RFA (Remote Function Actuator) module over the MS-CAN (Medium Speed Controller Area Network).

Visual Inspection and Diagnostic Pre-checks

- Door lock control switches

Pinpoint Test

1. CHECK THE BCM (Body Control Module) DTCs (Diagnostic Trouble Codes) FROM THE SELF-TEST

1. Using a scan tool, perform the BCM (Body Control Module) self-test.

Is DTC (Diagnostic Trouble Code) B126A:01 present?








2. VERIFY THE OPERATION OF BOTH DOOR LOCK CONTROL SWITCHES

1. Ignition OFF.

2. Press the lock and unlock button of both door lock control switches while observing the door lock operation.

Do the door locks operate only one way from both switches?








3. CHECK THE LOCK INPUT CIRCUIT FOR AN OPEN (SINGLE SWITCH INOPERATIVE)

1. Disconnect: Suspect Door Lock Control Switch.

2. Unlock the doors from the working door lock control switch.

3. For the LH (Left Hand) door lock control switch, connect a fused jumper wire:





4. For the RH (Right Hand) door lock control switch, connect a fused jumper wire:





Do the doors lock with the jumper wire?








4. CHECK THE UNLOCK INPUT CIRCUIT FOR AN OPEN (SINGLE SWITCH INOPERATIVE)

1. For the LH (Left Hand) door lock control switch, connect a fused jumper wire:





2. For the RH (Right Hand) door lock control switch, connect a fused jumper wire:





Do the doors unlock with the jumper wire?








5. CHECK THE LOCK INPUT OR THE UNLOCK INPUT CIRCUIT FOR AN OPEN (BOTH SWITCHES INOPERATIVE)

1. Disconnect: LH (Left Hand) Door Lock Control Switch.

2. Disconnect: BCM (Body Control Module) C2280C.

3. Measure:





Are the resistances less than 3 ohms?








6. CHECK FOR CORRECT BCM (Body Control Module) OPERATION

1. Ignition OFF.

2. Disconnect and inspect all BCM (Body Control Module) connectors.

3. Repair:

- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary

4. Reconnect the BCM (Body Control Module) connectors. Make sure they seat and latch correctly.

5. Operate the system and determine if the concern is still present.

Is the concern still present?