Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Backup Lamps PCB Relay B+ | 1 | 1 | -- | -- |
T/LAMP - BCK/UP Lamp Fuse | 1 | 1 | 1 | -- |
AUX/TRLR - BCK/UP Lamp Fuse | 1 | 1 | 1 | -- |
Backup Lamps PCB Relay Control | B2545 00 | 1 | 1 | -- |
Backup Lamps Control | 1 | 1 | 1 | -- |
Backup Lamps PCB Relay Ground | -- | 1 | -- | -- |
Backup Lamps Ground | -- | 1 | -- | -- |
1. Backup Lamps Malfunction | ||||
Circuit/System Description
Battery voltage is applied at all times to the backup lamp PCB relay which is an internal part of the body fuse block. When the PRNDL is placed in the REVERSE position, a GMLAN signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies battery voltage to the backup lamp relay control circuit energizing the relay. With the relay energized, battery voltage is applied through the switch side of the relay, the T/LAMP BCK/UP fuse, and the backup lamp supply voltage circuit to the left and right backup lamps. Or, the AUX/TRLR BCK/UP fuse and the supply voltage circuit to the backup alarm and the trailer connector.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
Backup Lamps Malfunction
- Ignition OFF, disconnect the X1 harness connector at the body fuse block.
- Test for less than 5 ohms between the ground circuit terminal 22 and ground.
- Connect a test lamp between the control circuit terminal 57 and ground.
- Ignition ON, command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- Igniton OFF, disconnect the inoperative backup lamp.
- Test for less than 5 ohms between the ground circuit terminal G and ground.
- Connect a test lamp between the backup lamp control terminal A and ground.
- Command the backup lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF between the commanded states.
- If the circuits test normal, replace the body fuse block.
| ⇒ | If greater then the specified range, test the ground circuit for and open/high resistance. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the ground circuit for a open/high resistance. |
| ⇒ | If the test lamp is always ON, test the control circuit for short to voltage. |
| ⇒ | If the test lamp is alway OFF, test the control circuit for a short to ground or and open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
