Pinpoint Test U: An Individual Reversing Lamp Is Inoperative

Reversing Lamps

Pinpoint Tests

Pinpoint Test U: An Individual Reversing Lamp Is Inoperative

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

Normal Operation

When the transmission is placed in REVERSE (R), voltage is routed through circuit CBP15 (BN/BU) to the reversing lamps. The reversing lamps are ground through circuit GD148 (BK/YE) (Explorer Sport Trac), circuit GD149 (BK/GY) (LH reversing lamp, Explorer/Mountaineer), or circuit GD151 (BK/GN) (RH reversing lamp, Explorer/Mountaineer).

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- Bulb holder



PINPOINT TEST U: AN INDIVIDUAL REVERSING LAMP IS INOPERATIVE

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.

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U1 CHECK FOR VOLTAGE TO THE REVERSING LAMP


- Ignition OFF.
- Disconnect: Inoperative Reversing Lamp.
- Apply the parking brake.
- Ignition ON.
- Select REVERSE.
- For Explorer, measure the voltage between the LH reversing lamp C487-2, circuit CBP15 (BN/BU), harness side and ground; or between the RH reversing lamp C488-2, circuit CBP15 (BN/BU), harness side and ground.




- For Mountaineer, measure the voltage between the LH reversing lamp C487-1, circuit CBP15 (BN/BU), harness side and ground; or between the RH reversing lamp C488-1, circuit CBP15 (BN/BU), harness side and ground.




- For Explorer Sport Trac, measure the voltage between the LH reversing lamp C451-3, circuit CBP15 (BN/BU), harness side and ground; or between the RH reversing lamp C461-3, circuit CBP15 (BN/BU), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to U2.

No
REPAIR circuit CBP15 (BN/BU) for an open. TEST the system for normal operation.

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U2 CHECK THE REVERSING LAMP GROUND CIRCUIT FOR AN OPEN


- Select PARK.
- Disconnect: Negative Battery Cable.
- Ignition OFF.
- For Explorer, measure the resistance between the LH reversing lamp C487-1, circuit GD149 (BK/GY), harness side and ground; or between the RH reversing lamp C488-1, circuit GD151 (BK/GN), harness side and ground.




- For Mountaineer, measure the resistance between the LH reversing lamp C487-2, circuit GD149 (BK/GY), harness side and ground; or between the RH reversing lamp C488-2, circuit GD151 (BK/GN), harness side and ground.




- For Explorer Sport Trac, measure the resistance between the LH reversing lamp C451-1, circuit GD148 (BK/YE), harness side and ground; or between the RH reversing lamp C461-1, circuit GD148 (BK/YE), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
INSTALL a new bulb holder. TEST the system for normal operation.

No
REPAIR the ground circuit in question for an open. TEST the system for normal operation.

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