Pinpoint Test P: Both Reversing Lamps Are Inoperative
Reversing Lamps
Pinpoint Tests
Pinpoint Test P: Both Reversing Lamps Are Inoperative
Refer to Wiring Diagram Set 11, Fuse and Relay Information for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 93, Reversing Lamps for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 140, Customer Access for schematic and connector information. Diagrams By Number
Normal Operation - All Engines
The reversing lamp relay coil is supplied voltage from the Battery Junction Box (BJB) fuse 77 (10A). The switched side is supplied voltage from the BJB fuse 58 (20A). When the reversing lamp relay is energized, voltage is routed to the reversing lamps (wagon) or the body builder connector (cutaway or stripped chassis vehicles). The reversing lamps share a ground with the stoplamps.
4.6L Engine
The reversing lamp relay coil ground is controlled by the digital Transmission Range (TR) sensor. When the transmission is placed in REVERSE (R), the digital TR sensor completes the path to ground, energizing the reversing lamp relay.
All Except 4.6L Engine
The reversing lamp relay coil ground is controlled by the PCM. When the transmission is placed in REVERSE (R), the PCM provides ground, energizing the reversing lamp relay.
- DTC P1910 (Reverse Lamp Control Circuit/Open) - sets when the PCM detects an open from the reversing lamps relay coil ground control circuit.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Reversing lamp relay
- Body builder equipment
- Digital TR sensor (4.6L engine)
- PCM (all except 4.6L engine)
PINPOINT TEST P: 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.
-------------------------------------------------
P1 CHECK STOPLAMP OPERATION
- Ignition OFF.
- Apply the brake pedal and observe the stoplamps.
- Do the stoplamps operate correctly?
Yes
GO to P2.
No
REFER to Stoplamps Special Tool(s) Used With Diagnostics.
-------------------------------------------------
P2 CHECK THE REVERSING LAMP RELAY
- Disconnect: Reversing Lamp Relay.
- Substitute a known good relay and recheck the operation of the reversing lamps.
- Do the reversing lamps illuminate?
Yes
REMOVE the known good relay. INSTALL a new reversing lamp relay. TEST the system for normal operation.
No
REMOVE the known good relay. GO to P3.
-------------------------------------------------
P3 CHECK FOR VOLTAGE TO THE REVERSING LAMP RELAY (COIL SIDE)
- Ignition ON.
- Measure the voltage between the reversing lamp relay pin 1, circuit CBB77 (WH), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to P4.
No
VERIFY the BJB fuse 77 (10A) is OK. If OK, REPAIR circuit CBB77 (WH) 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
-------------------------------------------------
P4 CHECK FOR VOLTAGE TO THE REVERSING LAMP RELAY (SWITCH SIDE)
- Ignition OFF.
- Measure the voltage between the reversing lamp relay pin 3, circuit SBB28 (GN/RD), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to P5.
No
VERIFY the BJB fuse 28 (20A) is OK. If OK, REPAIR circuit SBB28 (GN/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
-------------------------------------------------
P5 BYPASS THE REVERSING LAMP RELAY
- Connect a fused jumper wire between the reversing lamp relay pin 3, circuit SBB28 (GN/RD), BJB face side and the reversing lamp relay pin 5, circuit CLS28 (BU/WH), BJB face side.
- Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. GO to P7.
No
For wagon, REMOVE the jumper wire. REPAIR circuit CLS28 (BU/WH) for an open. TEST the system for normal operation.
For cutaway or stripped chassis vehicles, LEAVE the jumper wire connected. GO to P6.
-------------------------------------------------
P6 CHECK FOR VOLTAGE TO THE BODY BUILDER CONNECTOR
- Measure the voltage between the body builder C432-4, circuit CLS28 (BU/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
REMOVE the jumper wire. The vehicle is operating correctly. REFER to the body builder manual to continue diagnosis.
No
REMOVE the jumper wire. REPAIR circuit CLS28 (BU/WH) for an open. TEST the system for normal operation.
-------------------------------------------------
P7 CHECK THE REVERSING LAMP COIL GROUND CONTROLLED CIRCUIT FOR VOLTAGE
- Connect: Reversing Lamp Relay.
- Disconnect: Digital TR Sensor C167 (4.6L Engine).
- Disconnect: PCM C175t (5.4L Engine).
- Disconnect: PCM C1551b (6.8L Engine).
- Disconnect: PCM C1381t (6.0L Diesel).
- Ignition ON.
- For 4.6L engines, measure the voltage between the digital TR sensor C167-9, circuit CET41 (BN/YE), harness side and ground.
- For 5.4L engines, measure the voltage between the PCM C175t-34, circuit CET41 (BN/YE), harness side and ground.
- For 6.8L engines, measure the voltage between the PCM C1551b-24, circuit CET41 (BN/YE), harness side and ground.
- For 6.0L diesel engines, measure the voltage between the PCM C1381t-3, circuit CET41 (BN/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
For vehicles with a 4.6L engine, GO to P8.
For all other engines, GO to P9.
No
REPAIR circuit CET41 (BN/YE) for an open. TEST the system for normal operation.
-------------------------------------------------
P8 BYPASS THE DIGITAL TR SENSOR
- Ignition OFF.
- Connect a fused jumper wire between the digital TR sensor C167-9, circuit CET41 (BN/YE), harness side and the digital TR sensor C167-11, circuit GD123 (BK/GY), harness side.
- Ignition ON.
- Do the reversing lamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new digital TR sensor. REFER to Automatic Transaxle/Transmission - 4R70E/4R75E 4R70E/4R75E. TEST the system for normal operation.
No
REMOVE the jumper wire. REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
-------------------------------------------------
P9 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all 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. REFER to Electronic Engine Controls 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.
-------------------------------------------------