Pinpoint Test R: The Reversing Lamps Are On Continuously
Reversing Lamps
Pinpoint Tests
Pinpoint Test R: The Reversing Lamps Are On Continuously
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
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) and the auto-dimming interior mirror (if equipped).
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 a short to ground from the reversing lamps relay coil ground control circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Reversing lamp relay
- Body builder equipment
- Auto-dimming interior mirror
- Digital TR sensor (4.6L engine)
- PCM (all except 4.6L engine)
PINPOINT TEST R: THE REVERSING LAMPS ARE ON CONTINUOUSLY
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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R1 CHECK THE TRAILER REVERSING LAMP CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: BJB Fuse 58 (15A).
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
GO to R2.
No
REPAIR circuit CAT03 (GY/BN) for a short to voltage. TEST the system for normal operation.
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R2 ISOLATE THE CAUSE OF THE CONCERN
- Ignition OFF.
- Disconnect: Reversing Lamp Relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
For stripped chassis or cutaway vehicles not equipped with an auto-dimming interior mirror, GO to R4.
For wagon or cutaway vehicles equipped with an auto-dimming interior mirror, GO to R3.
For wagon not equipped with an auto dimming interior mirror, REPAIR circuit CET41 (BU/WH) for a short to voltage. TEST the system for normal operation.
No
GO to R5.
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R3 CHECK THE REVERSING LAMP SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Auto-Dimming Interior Mirror C9039 or 9012.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
For cutaway vehicles, GO to R4.
For wagon, REPAIR circuit CET41 (BU/WH) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new auto-dimming interior mirror. REFER to Rear View Mirrors Interior Rear View Mirror. TEST the system for normal operation.
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R4 ISOLATE THE VEHICLE CHASSIS AS THE CAUSE OF THE CONCERN
- Ignition OFF.
- Disconnect: Body Builder C432.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
The vehicle is operating correctly. REFER to the body builder manual to continue diagnosis.
No
REPAIR circuit CET41 (BU/WH) for a short to voltage. TEST the system for normal operation.
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R5 CHECK THE REVERSING LAMP RELAY
- Ignition OFF.
- Substitute a known good reversing lamp relay
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
REMOVE the known good relay. GO to R6.
No
REMOVE the known good relay. INSTALL a new reversing lamp relay. TEST the system for normal operation.
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R6 CHECK THE REVERSING LAMP COIL GROUND CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- 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.
- Do the reversing lamps continue to illuminate?
Yes
REPAIR circuit CET41 (BN/YE) for a short to ground. TEST the system for normal operation.
No
For vehicles with a 4.6L engine, INSTALL a new digital TR sensor. REFER to Automatic Transaxle/Transmission - 4R70E/4R75E 4R70E/4R75E. TEST the system for normal operation.
For all other engines, GO to R7.
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R7 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.
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