Diagnostic Routine A

Diagnostic Routine A

Diagnostic Overview

All Door Locks Are Inoperative

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

Normal Operations and Fault Conditions

The BCM (Body Control Module) supplies voltage to the lock all relay, the unlock driver door relay or unlock all relay based upon input from the door lock control switches, the RKE (Remote Keyless Entry) transmitter, or the keyless entry keypad. Upon a lock request, the BCM (Body Control Module) supplies voltage on the all door lock circuit and ground on the driver and passenger door unlock circuits. Upon an unlock request, the voltage and ground are reversed on the previously listed circuits. When the door lock and unlock relays are not energized they are connected to ground. A dedicated BCM (Body Control Module) ground circuit is provided only for the lock and unlock relays.

NOTE: The lock all, unlock driver door, and the unlock all relays are internal to the BCM (Body Control Module) and are non-serviceable.

Visual Inspection and Diagnostic Pre-checks

BCM (Body Control Module) fuse 20 (20A)

Pinpoint Test

1. CHECK THE DTCs (Diagnostic Trouble Codes) FROM THE BCM (Body Control Module) 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. Press the lock and unlock buttons on both door lock control switches while observing the door lock operation.

Are the door locks inoperative from both switches?








3. VERIFY ALL DOOR LOCKS ARE INOPERATIVE

1. Press the lock and unlock buttons from a door lock control switch while observing the door locks.

Are all the door locks inoperative from both switch positions (lock and unlock)?








4. CHECK THE POWER DOOR LOCK RELAY GROUND CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect BCM (Body Control Module) C2280D.

3. Measure:





Is the resistance less than 3 ohms?








5. CHECK THE ALL DOOR LOCK CIRCUIT FOR AN OPEN

1. Disconnect LH (Left Hand) Front Door Lock Actuator.

2. Measure:





Is the resistance less than 3 ohms?








6. CHECK THE ALL LOCK CIRCUIT FOR A SHORT TO GROUND

1. Install a new BCM (Body Control Module) fuse 20 (20A).

2. Operate the door lock actuators by pressing LOCK on the door lock control switch.

Is the BCM (Body Control Module) fuse 20 (20A) OK?








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

1. Ignition OFF.

2. Disconnect all the BCM (Body Control Module) connectors.

3. Repair:

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

4. Connect all the BCM (Body Control Module) connectors and make sure they seat correctly.

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

Is the concern still present?