Pinpoint Test U: Both Reversing Lamps Are Inoperative
Reversing Lamps
Pinpoint Test U: Both Reversing Lamps Are Inoperative
Normal Operation
The PCM (gasoline engine) or the Transmission Control Module (TCM) (diesel engine) monitors the transmission. When the transmission is in REVERSE, the PCM or TCM (Transmission Control Module) 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 (Body Control Module) receives the message indicating the transmission is in REVERSE and the ignition is in the RUN state, the BCM (Body Control Module) 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.
On vehicles with a manual transmission, the reversing lamp switch is monitored by the PCM.
- DTC B1277:11 (Reverse Lamp: Circuit Short To Ground)- a DTC that sets when the BCM (Body Control Module) detects a short to ground from the reversing lamp output circuit.
- DTC B1277:15 (Reverse Lamp: Circuit Short To Battery or Open)- a DTC that sets when the BCM (Body Control Module) detects an open from the reversing lamp output circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Reversing lamp switch (manual transmission)
- PCM
- BCM (Body Control Module)
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.
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 J Pinpoint Test J: One Or More Stoplamps Are Inoperative.
U2 CHECK THE BCM (Body Control Module) OUTPUT
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- Select the BCM (Body Control Module) reverse lamps active command (RVRS_LMPS). Command the reverse lamps on then off.
Do the reversing lamps illuminate when commanded on?
Yes
If equipped with an automatic transmission, REFER to Automatic Transmission/Transaxle &/or Transmission Control Systems to diagnose a Transmission Range (TR) concern.
If equipped with a manual transmission, GO to U3.
No
GO to U6.
U3 BYPASS THE REVERSING LAMP SWITCH
- Ignition OFF.
- Disconnect: Reversing Lamp Switch C169.
- Connect a fused jumper wire between the reversing lamp switch C169-1, circuit CET47 (GY/OG or BU), harness side and the reversing lamp switch C169-2, circuit GD124 or GD120 (BK/VT or BK), harness side.
- Ignition ON.
Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new reversing lamp switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to U4.
U4 BYPASS THE REVERSING LAMP SWITCH GROUND CIRCUIT
- Connect a fused jumper wire between the reversing lamp switch C169-1, circuit CET47 (GY/OG or BU), harness side and ground.
Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. REPAIR circuit GD124 or GD120 (BK/VT or BK) for an open. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to U5.
U5 CHECK THE REVERSING LAMP SWITCH INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175T.
- Measure the resistance between the reversing lamp switch C169-1, circuit CET47 (GY/OG or BU), harness side and the PCM C175T-7, circuit CET47 (GY/OG or BU), harness side.
Is the resistance less than 5 ohms?
Yes
GO to U7.
No
REPAIR circuit CET47 (GY/OG or BU) for an open. TEST the system for normal operation.
U6 BYPASS THE BCM (Body Control Module)
NOTE: If the jumper wire fails, refer to the Wiring Diagrams to identify the possible causes of the circuit short. After the repair: 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 (Body Control Module). Test the system for normal operation. [1][2]Diagrams By Number
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280D.
- Connect a fused jumper wire between the BCM (Body Control Module) C2280D-13, circuit CLS28 (BU/WH), harness side and battery positive.
Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. GO to U8.
No
REMOVE the jumper wire. REPAIR circuit CLS28 (BU/WH) for an open. TEST the system for normal operation.
U7 CHECK FOR CORRECT PCM OPERATION
- Disconnect the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the PCM 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 PCM. 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.
U8 CHECK FOR CORRECT BCM (Body Control Module) OPERATION
- Disconnect the BCM (Body Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the BCM (Body Control Module) 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 (Body Control Module). 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.