Pinpoint Test V: Both Reversing Lamps Are Inoperative
Reversing Lamps
Pinpoint Tests
Pinpoint Test V: Both Reversing Lamps Are Inoperative
Refer to Wiring Diagram Set 93, Reversing Lamps for schematic and connector information. Diagrams By Number
Normal Operation
Voltage is supplied from the Battery Junction Box (BJB) fuse 29 (20A) to the switched side of the reversing lamps relay. The reversing lamps relay coil power is supplied by the Transmission Control Module (TCM) (also called a main control valve body for Expedition and a mechatronic assembly for Navigator). The reversing lamps relay coil ground is controlled by the TCM. When the reversing lamps relay is energized, voltage is routed to the reversing lamps.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Reversing lamps relay
- TCM
PINPOINT TEST V: 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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V1 CHECK THE REVERSING LAMPS RELAY
- Ignition OFF.
- Disconnect: Reversing Lamps Relay.
- Substitute a known good relay.
- Apply the parking brake.
- Ignition ON.
- Select REVERSE.
- Do the reversing lamps illuminate?
Yes
REMOVE the known good relay. INSTALL a new reversing lamps relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to V2.
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V2 CHECK FOR VOLTAGE TO THE REVERSING LAMPS RELAY
- Select PARK.
- Ignition OFF.
- Measure the voltage between the reversing lamps relay pin 3, circuit SBB29 (GY/RD), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to V3.
No
VERIFY the BJB fuse 29 (20A) is OK. If OK, REPAIR circuit SBB29 (GY/RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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V3 BYPASS THE REVERSING LAMPS RELAY
- Connect a fused jumper wire between the reversing lamps relay pin 3, circuit SBB29 (GY/RD), BJB face side and the reversing lamps relay pin 5, circuit CLS10 (GN/BN), BJB face side.
- Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. GO to V4.
No
REMOVE the jumper wire. REPAIR circuit CLS10 (GN/BN) for an open. TEST the system for normal operation.
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V4 CHECK THE REVERSING LAMPS RELAY COIL CIRCUITS FOR A SHORT TO GROUND
- Disconnect: TCM C1548.
- Measure the resistance between the reversing lamps relay pin 1, circuit CAT03 (GY/BN), BJB face side and ground; and between the reversing lamps relay pin 2, circuit RET24 (BN/BU), BJB face side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
GO to V5.
No
REPAIR the circuit in question for a short to ground. CLEAR the DTCs. REPEAT the self-test.
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V5 CHECK THE REVERSING LAMPS RELAY COIL CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between the reversing lamps relay pin 1, circuit CAT03 (GY/BN), BJB face side and ground; and between the reversing lamps relay pin 2, circuit RET24 (BN/BU), BJB face side and ground.
- Is any voltage present?
Yes
REPAIR the circuit in question for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
GO to V6.
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V6 CHECK THE REVERSING LAMPS RELAY COIL CIRCUITS FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the reversing lamps relay pin 1, circuit CAT03 (GY/BN), BJB face side and the TCM C1548-7, circuit CAT03 (GY/BN), harness side.
- Measure the resistance between the reversing lamps relay pin 2, circuit RET24 (BN/BU), BJB face side and the TCM C1548-15, circuit RET24 (BN/BU), harness side.
- Are the resistances less than 5 ohms?
Yes
GO to V7.
No
REPAIR the circuit in question for an open. CLEAR the DTCs. REPEAT the self-test.
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V7 CHECK FOR CORRECT TCM OPERATION
- Disconnect the TCM connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the TCM connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new TCM. REFER to Automatic Transaxle/Transmission - 6R80 Mechatronic Assembly. 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. CLEAR any DTCs. REPEAT the self-test.
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