Circuit Description
When the body control module (BCM) receives a signal requesting to illuminate the backup lamps, battery voltage is sent directly from the BCM through the backup lamp supply voltage circuit to the backup lamps.
Voltage for the backup lamp supply voltage circuit as well as the courtesy lamp supply voltage circuit is from the left instrument panel fuse block TBC 2B 15-amp fuse directly through the BCM to these circuits.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2550 Backup Lamps Control Circuit
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | When the BCM receives a backup lamp request signal and the backup lamp supply voltage circuit is shorted to ground |
| • | When the BCM is not receiving a backup lamp request signal and the backup lamp supply voltage circuit is open or shorted to voltage |
| • | There is a loss of the instrument panel fuse block TBC 2B battery supply voltage to the BCM for 1 second. |
Action Taken When the DTC Sets
The backup lamps will not operate.
Conditions for Clearing the MIL/DTC
| • | This DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
| • | Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | A short to ground on the backup lamp supply voltage circuit, courtesy lamp supply voltage circuit OR the TBC 2B battery positive voltage circuit to the BCM will open the TBC 2B fuse in the left instrument panel fuse block. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the problem exists in the wiring or the BCM.
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This step determines if the problem exists in the wiring or the BCM.
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After replacement of the BCM you must calibrate the new module for proper operation.
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views | |||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||
2 | Inspect the TBC 2B fuse in the instrument panel fuse block. Is the fuse open? | Go to Step 3 | Go to Step 4 | ||||||||
Test the following circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition? | Go to Step 6 | Go to Step 5 | |||||||||
Test the backup lamp supply voltage circuit for the following conditions:
Did you find and correct the condition? | Go to Step 6 | Go to Step 5 | |||||||||
Replace the BCM. Refer to Control Module References . Did you complete the replacement? | Go to Step 6 | -- | |||||||||
6 |
Does the DTC reset? | Go to Step 2 | System OK | ||||||||
