Body Control Module (BCM)
SYSTEM DESCRIPTIONWhen you press any button on the keyless entry transmitter, the transmitter sends a radio frequency signal to the Remote Control Door Lock Receiver (RCDLR).
The RCDLR interfaces with the Body Control Module (BCM) in order to perform the door lock/unlock functions. On the vehicles equipped with the content theft deterrent (BCM type 4), the RCDLR interfaces with the BCM in order to perform the alarm functions. The RCDLR sends a digital message to the BCM through CKT 377. The RCDLR determines the type of message sent to the BCM based on the button pressed on the keyless entry transmitter.
The BCM determines what functions to perform (door lock/unlock, alarm) based on the messages received from the RCDLR.
CONDITIONS FOR SETTING THE DTC
The BCM detects an open, a short to B+ or a short to ground in CKT 377.
ACTION TAKEN WHEN THE DTC SETS
^ The BCM sets the Diagnostic Trouble Code (DTC) 8.
^ The keyless entry system remains inoperative. The rear compartment lid release may still be operational because the RCDLR operates the rear compartment lid directly without using the BCM.
CONDITIONS FOR CLEARING THE DTC
^ An open, a short to B+ or a short to ground in CKT 377 is no longer present between the BCM and the RCDLR.
^ After the repairs are completed, refer to Body Control Module Diagnostic Information
DIAGNOSTIC AIDS
^ Inspect for an open, a short to B+ or a short to ground in CKT 377.
^ A faulty horn RCDLR.
^ Perform the following test while moving the wiring and connectors. This will cause the malfunction to appear.
BCM INPUT/OUTPUT TEST PROCEDURE
1. Turn the IP dimmer switch OFF.
2. Turn the ignition switch to the OFF position.
3. Remove the MALL PGM fuse.
4. Turn the ignition switch to the ACC position. The BCM will sound a chime the number of times equivalent to the BCM type installed on the vehicle.
5. Within 1 second, turn the ignition switch from the ACC position, to the OFF position then back to the ACC position.
The BCM will sound any DTCs that are stored.
6. Turn the IP dimmer switch to the DOME position. The BCM enters the input/Output test. There are 7 steps in the Input/Output test:
^ Test 1 de-energizes CKT 1393 (protected courtesy lamp output).
^ Test 2 energizes CKT 1393.
^ Test 3 grounds CKT 690 (courtesy lamps control).
^ Test 4 energizes the theft deterrent relay for 1 second by grounding CKT 352 and turns on the headlamps (BCM type 4 only).
^ Test 5 energizes the horn relay for 25 ms by grounding CKT 28 and sounds the horn (BCM type 4 only).
^ Test 6 turns on the theft deterrent indicator lamp by grounding CKT 749 (BCM type 4 only).
^ Test 7 turns off the theft deterrent indicator lamp by opening CKT 749 (BCM type 4 only).
The BCM completes the steps of the Input/Output test in numerical order.
In order to move to the next test, cycle the IP dimmer switch from DOME to OFF then back to DOME. The BCM will sound a chime a number of times equivalent to the Input/Output test number above. The Input/Output test sequence repeats until the ignition switch is turned to the OFF position.
When the BCM is performing the Input/output test the BCM will sound the chime when any of the keyless remote transmitter buttons is pressed (BCM type 3 and 4 only). This test inspects and ensures the BCM is receiving commands from the keyless entry transmitter via the RCDLR.
Diagnostic Chart (Part 1 Of 2):
Diagnostic Chart (part 2 Of 2):
TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
1. Always perform the BCM diagnostic system check before attempting to diagnose this DTC.
2. This step determines whether the malfunction is related to a fault within the Remote Control Door Lock Receiver (RCDLR) and not due to a faulty CKT 377.
3. This step determines whether the malfunction is intermittent and not currently present.
4. This step checks for an open in CKT 377.
5. This step checks for a short to ground in CKT 377.
6. This step checks for a short to B+ in CKT 377.
7. This step determines whether the malfunction is intermittent and not related to a faulty BCM.