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Pinpoint Test X: The Reversing Lamps Are On Continuously




Reversing Lamps

Pinpoint Tests

Pinpoint Test X: The Reversing Lamps Are On Continuously

Refer to Wiring Diagram Set 93, Reversing Lamps for schematic and connector information. Diagrams By Number

Normal Operation - 4R70E/4R75E Transmission

When the transmission is in REVERSE (R), the digital Transmission Range (TR) sensor routes voltage to the reversing lamps relay coil and the auto-dimming interior mirror. When the reversing lamps relay is energized, voltage is routed to the reversing lamps and Battery Junction Box (BJB) fuse 58 (15A). The BJB fuse 58 (15A) routes voltage to the trailer tow connector.

6R80 Transmission/5.4L Engine Combination

The reversing lamps relay coil power and ground is supplied and controlled by the Transmission Control Module (TCM) (also called the mechatronic assembly). When the transmission is in REVERSE (R), the TCM energizes the reversing lamps relay. When the reversing lamps relay is energized, voltage is routed to the reversing lamps, the BJB fuse 55 (5A) and the BJB fuse 58 (15A). The BJB fuse 55 (5A) routes voltage to the auto-dimming interior mirror and the BJB fuse 58 (15A) routes voltage to the trailer tow connector.

6R80 Transmission/6.2L Engine Combination

The reversing lamps relay coil is supplied voltage when the PCM relay is energized (ignition system is in the RUN state). When the transmission is in REVERSE (R), the PCM provides ground to energize the reversing lamps relay. When the reversing lamps relay is energized, voltage is routed to the reversing lamps, the BJB fuse 55 (5A) and the BJB fuse 58 (15A). The BJB fuse 55 (5A) routes voltage to the auto-dimming interior mirror and the BJB fuse 58 (15A) routes voltage to the trailer tow connector.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- Reversing lamps relay
- Auto-dimming interior mirror
- Digital TR sensor (4R70E/4R75E transmission)
- TCM (6R80 transmission/5.4L engine combination)
- PCM (6R80 transmission/6.2L engine combination)



PINPOINT TEST X: 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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X1 CHECK THE REVERSING LAMPS RELAY OUTPUT


- Disconnect: Reversing Lamps Relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
For vehicles with a 4R70E/4R75E transmission, GO to X5.

For vehicles with a 6R80 transmission, GO to X8.

No
For vehicles with a 4R70E/4R75E transmission, GO to X2.

For vehicles with a 6R80 transmission, GO to X6.

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X2 CHECK FOR VOLTAGE TO THE REVERSING LAMPS RELAY COIL


- Measure the voltage between the reversing lamp relay pin 1, circuit CET47 (BU), BJB face side and ground.




- Is any voltage present?

Yes
If equipped with an auto-dimming interior mirror, GO to X3.

If not equipped with an auto-dimming interior mirror, GO to X4.

No
INSTALL a new reversing lamps relay. TEST the system for normal operation.

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X3 CHECK THE AUTO-DIMMING INTERIOR MIRROR (4R70E/4R75E TRANSMISSION)


- Ignition OFF.
- Disconnect: Auto-Dimming Interior Mirror C911, C9012 or C9039.
- Connect: Reversing Lamps Relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
GO to X4.

No
INSTALL a new auto-dimming interior mirror. REFER to Mirrors. TEST the system for normal operation.

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X4 CHECK THE DIGITAL TR SENSOR


- Ignition OFF.
- Disconnect: Digital TR Sensor C167.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
REPAIR circuit CET47 (BU) for a short to voltage. TEST the system for normal operation.

No
INSTALL a new digital TR sensor. REFER to Automatic Transmission/Transaxle &/or Transmission Control Systems. TEST the system for normal operation.

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X5 CHECK THE TRAILER TOW REVERSING LAMP VOLTAGE SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE (4R70E/4R75E TRANSMISSION)


- Disconnect: BJB Fuse 58 (15A).
- Do the reversing lamps continue to illuminate?

Yes
REPAIR circuit CAT16 (GY/BN) for a short to voltage. TEST the system for normal operation.

No
REPAIR circuit CAT03 (GY/BN) for a short to voltage. TEST the system for normal operation.

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X6 CHECK THE REVERSING LAMPS RELAY


- Ignition OFF.
- Substitute a known good relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
REMOVE the known good relay.

For vehicles with a 5.4L engine, GO to X11.

For vehicles with a 6.2L engine, GO to X7.

No
REMOVE the known good relay. INSTALL a new reversing lamps relay. TEST the system for normal operation.

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X7 CHECK THE REVERSING LAMPS RELAY GROUND CONTROLLED CIRCUIT FOR A SHORT TO GROUND


- Ignition OFF.
- Connect: Reversing Lamps Relay.
- Disconnect: PCM C1381b.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
REPAIR circuit CLS28 (BU/WH) for a short to ground. TEST the system for normal operation.

No
GO to X12.

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X8 CHECK THE TRAILER TOW REVERSING LAMP VOLTAGE SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE


- Disconnect: BJB Fuse 58 (15A).
- Do the reversing lamps continue to illuminate?

Yes
GO to X9.

No
REPAIR circuit CAT03 (GY/BN) for a short to voltage. TEST the system for normal operation.

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X9 CHECK THE AUTO-DIMMING INTERIOR MIRROR REVERSE SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE


- Disconnect: BJB Fuse 55 (5A).
- Do the reversing lamps continue to illuminate?

Yes
REPAIR circuit CAT16 (GY/BN) for a short to voltage. TEST the system for normal operation.

No
GO to X10.

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X10 CHECK THE AUTO-DIMMING INTERIOR MIRROR


- Connect: BJB Fuse 55 (5A).
- Ignition OFF.
- Disconnect: Auto-Dimming Interior Mirror C911, C9012 or C9039.
- Ignition ON.
- Do the reversing lamps continue to illuminate?

Yes
REPAIR circuit CET47 (BU) for a short to voltage. TEST the system for normal operation.

No
INSTALL a new auto-dimming interior mirror. REFER to Mirrors. TEST the system for normal operation.

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X11 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 Transmission/Transaxle &/or Transmission Control Systems, 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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X12 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. REFER to Computers and Control Systems. 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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