The body control module (BCM) provides diagnostics to assist service technicians during troubleshooting. The BCM has the following diagnostic capabilities when entering the diagnostics mode:
| • | Diagnostic trouble codes (DTCs) |
| • | Input/Output tests |
Entering The Feature Customization Mode
When you perform BCM diagnostics, enter the feature customization mode. During this mode, the BCM identifies itself. This ensures that the option content of the vehicle matches the capabilities of the BCM.
Complete the following steps in order to enter the feature customization mode:
- Turn the ignition switch to the OFF position.
- Remove the MALL PGM fuse.
- Turn the ignition switch to the ACC position.
Upon entering the feature customization mode, the BCM flashes the fasten belts indicator and sounds the chime 2, 3 or 4 times. The number of chimes is equal to the BCM type used on the vehicle. Ensure that the BCM installed on the vehicle is compatible with all the features on the vehicle. If an incorrect BCM is installed, replace the BCM with the correct type.
At this point, the following vehicle systems have features that can be customized:
| • | The interior lighting |
| • | The automatic door lock |
| • | The keyless entry |
| • | The content theft deterrent |
Entering The Diagnostics Mode
Complete the following steps in order to enter the diagnostics mode:
- Ensure that the BCM is in the feature customization mode.
- Turn the ignition switch from the ACC position to the OFF position, then back to the ACC position within 1 second.
Perform the following procedure in order to confirm the BCM has entered the diagnostics mode:
- Ensure that all of the vehicle doors are closed.
- Open and close any one of the doors.
- Fasten and release the driver seat belt.
The BCM sounds the chime when it receives an input signal such as opening a door or fastening the drivers seat belt when the BCM is in the diagnostics mode.
The following actions occur when the diagnostics mode is entered:
| • | The BCM flashes the fasten belts indicator. |
| • | The BCM sounds the chime a number of times equal to the DTCs that are stored in the memory. |
If no DTCs are stored, the BCM does not flash the fasten belts indicator nor sounds the chime.
The BCM flashes and sounds the first DTC with the lowest number. The BCM pauses and continues with the next DTC until all the DTCs are read. Once all the DTCs are read, the BCM repeats this sequence 3 times.
If there are DTCs in the memory, record the DTCs.
Identifying The Diagnostic Trouble Codes
DTC | Definition |
|---|---|
1 | Fasten belt indicator lamp control circuit shorted to B+ or ground |
2 | Power output circuit to courtesy lamps shorted to B+ or ground |
3 | Courtesy lamps ground control circuit shorted to B+ |
4 | RAP relay control circuit shorted to B+ or ground |
6 | Theft deterrent relay control circuit shorted to B+ or ground |
7 | Horn relay control circuit shorted to B+ or ground |
8 | RFA link circuit open or shorted to B+ or ground |
Clearing Diagnostic Trouble Codes (DTCs)
In order to erase the DTCs stored in the BCM, press and hold the UNLOCK button on either power door lock switch for 4 seconds.
Entering The Input/Output Test
After the BCM reads all of the DTCs in the memory, the BCM enters the Input /Output test.
The BCM flashes the fasten belts indicator and sounds the chime once when operating one of the following inputs:
| • | All the reading courtesy lamp switches |
| • | The door lock cylinders |
| • | The drivers door lock ajar switch |
| • | The drivers fasten seat belt switch |
| • | The driver information display (DID) |
| • | The headlamps OFF switch |
| • | The IP compartment lamp switch |
| • | The keyless entry requests for door lock/unlock |
| • | The passenger door lock ajar switch |
| • | The power door lock switches |
| • | The rear compartment courtesy lamp switch |
| • | The shock sensor |
| • | The sunshade illuminated mirrors |
| • | The trip calculator |
| • | The turn signal switch |
If the BCM does not provide a chime feedback, one of the following conditions exists:
| • | An open in the circuit |
| • | A short in the circuit |
| • | A faulty component |
Complete the following steps in order to test the BCM outputs:
- Ensure the BCM is in the diagnostic mode.
- Turn the IP dimmer switch to the DOME position.
The BCM enters the output test. The output test has 7 steps:
| • | Test 1 de-energizes CKT 1993 and turns off all of the interior lamps. |
| • | Test 2 energizes CKT 1393 and provides power to all of the interior lamps. |
| • | Test 3 grounds CKT 690 and turns on all of the courtesy lamps. |
| • | Test 4 energizes the theft deterrent relay for 1 second by grounding CKT 352 and turns on all of 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 output steps in numerical order.
In order to move to the next test, cycle the IP dimmer switch from the dome position, to OFF then back to DOME. The BCM sounds the chime a number of times equivalent to the output test number above.
Exiting Diagnostics
Perform the following procedure in order to exit the BCM diagnostics mode and return to normal BCM operation:
- Turn the ignition switch to the OFF position.
- Reinstall the MALL PGM fuse.
- Turn the ignition switch to the RUN position.
