Pinpoint Test U: Both Reversing Lamps Are Inoperative
Reversing Lamps
Pinpoint Tests
Pinpoint Test U: Both Reversing Lamps Are Inoperative
Refer to Wiring Diagram Set 93, Reversing Lamps for schematic and connector information. Diagrams By Number
Normal Operation
The PCM monitors the transmission gear status. When the transmission is in reverse, the PCM sends a message to the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN), indicating the transmission is in reverse. When the BCM receives the message indicating the transmission is in reverse and the ignition is in RUN, the BCM provides voltage to the reversing lamps.
The reversing lamps share the fused power supply with the high mounted stoplamp and the ground circuit with the rear stoplamps.
- DTC B1277:11 (Reverse Lamp: Circuit Short To Ground) - This DTC sets when the BCM detects a short to ground from the reversing lamp output circuit.
- DTC B1277:15 (Reverse Lamp: Circuit Short To Battery or Open) - This DTC sets when the BCM detects an open from the reversing lamp output circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Transmission gear input
- BCM
PINPOINT TEST U: BOTH REVERSING LAMPS ARE INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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U1 CHECK THE STOPLAMP OPERATION
- Ignition OFF.
- Apply the brake pedal while observing all the stoplamps.
- Do the stoplamps illuminate?
Yes
GO to U2.
No
GO to Pinpoint Test I Pinpoint Test I: All The Stoplamps Are Inoperative.
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U2 CHECK THE BCM OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM DataLogger.
- Select the BCM reverse lamps active command (RVRS_LMPS). Command the reverse lamps on then off.
- Do the reversing lamps illuminate when commanded on?
Yes
REFER to Automatic Transaxle/Transmission - 6R80 Testing and Inspection to diagnose a Transmission Range (TR) concern.
No
GO to U3.
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U3 BYPASS THE BCM
NOTE: If the jumper wire fails, refer to the Wiring Diagrams to identify the possible causes of the circuit short. After the repair: Diagrams By Number
If no DTCs are present, test the system for normal operation. If DTC U1000:00 is present, clear the DTCs and repeat the self-test (required to enable the reversing lamp output driver if DTC U1000:00 is present). Test the system for normal operation.
If DTC U3000:49 is present, install a new BCM. Refer to Multifunction Electronic Modules Service and Repair. Test the system for normal operation.
- Ignition OFF.
- Disconnect: BCM C2280D.
- Connect a fused jumper wire between the BCM C2280D-13, circuit CLS28 (BU/WH), harness side and battery positive.
- Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. GO to U4.
No
REMOVE the jumper wire. REPAIR circuit CLS28 (BU/WH) for an open. TEST the system for normal operation.
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U4 CHECK FOR CORRECT BCM OPERATION
- Disconnect the BCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the BCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new BCM. REFER to Multifunction Electronic Modules Service and Repair. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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