Circuit Description
The body control module (BCM) provides a 12 volt output to the courtesy lamps when the BCM is in the awake state. The courtesy lamp return is through CKT 156 (WHT) or CKT 157 (GRY) and is active when commanded by one of the following components:
| • | The dome lamp switch |
| • | The LF door jamb switch |
| • | The RF door jamb switch |
| • | The LR door jamb switch |
| • | The RR door jamb switch |
| • | The cargo door jamb switch |
| • | The liftgate jamb switch |
The BCM controls the courtesy lamp feed circuit and distributes power to the following components:
| • | The dome lamps |
| • | The courtesy/reading lamps |
| • | IP compartment box lamp |
| • | The sunshade mirror lamps |
| • | The automatic day/night mirror |
| • | The power mirrror switch |
Conditions for Setting the DTC
| • | CKT 149 is open due to defective courtesy fuse 3, wiring or harness connector. |
| • | CKT 40 (courtesy lamps feed) is shorted to the ground for greater than 50 milliseconds, while the BCM is in an awake state. |
| • | The BCM is defective. |
Action Taken When the DTC Sets
| • | DTC 21 will set. |
| • | There will be no courtesy lighting in the vehicle. |
| • | The IP dimmer switch is inoperative. |
| • | The BCM will read out a series of flash DTCs upon entering diagnostic mode. |
Conditions for Clearing the MIL/DTC
The fault is corrected and the DTC memory is cleared.
Diagnostic Aids
In order to retrieve the DTC's from the BCM, refer to Diagnostic Trouble Code (DTC) Displaying in Body Control System.
If the only DTC that flashes is a history code (DTC 31), the problem may be intermittent. Try performing the test shown while "wiggling" wiring and connectors. This action can often cause the fault to appear. Test for poor connections at the BCM connector, which could cause an open or an intermittent fault.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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This step tests for an open courtesy fuse 3.
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If courtesy fuse 3 is open, this step tests for a short to the ground on CKT 149.
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If courtesy fuse 3 is OK, this step tests for a short to ground in CKT 40.
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Prompts replacement of the BCM.
Important: Inspect for the proper installation of aftermarket electronic equipment which may affect the integrity of the system.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Check CTSY Fuse 3. Is Fuse 3 open? | -- | Go to Step 2 | Go to Step 4 | |
Test CKT 149 (DK BLU/WHT) for a short to ground or an open. Is CKT 149 open or shorted? | -- | Go to Step 3 | Go to Step 4 | |
3 | Repair short to ground or open in CKT 149 between IP fuse block and BCM. Refer to Wiring Repairs in Wiring Systems. Is repair complete? | -- | System OK | -- |
Test CKT 40 (ORN) for a short to ground. Is CKT 40 (ORN) shorted? | -- | Go to Step 5 | Go to Step 6 | |
5 | Repair short to ground in CKT 40 (ORN). Refer to Wiring Repairs in Wiring Systems. Is repair complete? | -- | System OK | -- |
Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Is the repair complete? | -- | System OK | -- |
