Pinpoint Test AA: The Trailer Parking Lamps Are Inoperative

Trailer Lamps

Pinpoint Tests

Pinpoint Test AA: The Trailer Parking Lamps Are Inoperative

Refer to Wiring Diagram Set 95 (Escape/Mariner, Escape Hybrid/Mariner Hybrid), Trailer/Camper Adapter for schematic and connector information. Diagrams By Number

Normal Operation

The trailer tow parking lamp relay coil receives voltage when the vehicle parking lamps are illuminated. The Battery Junction Box (BJB) fuse 8 (20A) supplies voltage to the trailer tow parking lamp relay switch side. When the trailer tow parking lamp relay is energized, the voltage is routed to the trailer tow connector.

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- Trailer tow parking lamp relay
- Trailer


PINPOINT TEST AA: THE TRAILER PARKING 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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AA1 CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR

- Ignition OFF.
- Disconnect: Trailer Tow C439.
- Place the headlamp switch in the PARKING LAMPS ON position.
- Measure the voltage between the trailer tow C439-3, circuit CAT11 (BN), harness side and ground.





- Is the voltage greater than 10 volts?

Yes
The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.

No
GO to AA2.

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AA2 CHECK THE TRAILER TOW PARKING LAMP RELAY

- Disconnect: Trailer Tow Parking Lamp Relay.
- Substitute a known good relay.
- Measure the voltage between the trailer tow C439-3, circuit CAT11 (BN), harness side and ground.





- Is the voltage greater than 10 volts?

Yes
REMOVE the known good relay. INSTALL a new trailer tow parking lamp relay. TEST the system for normal operation.

No
REMOVE the known good relay. GO to AA3.

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AA3 CHECK FOR VOLTAGE TO THE TRAILER TOW PARKING LAMP RELAY COIL

- Place the headlamp switch in the PARKING LAMPS ON position.
- Measure the voltage between the trailer tow parking lamp relay pin 2, circuit CLS30 (VT/WH), BJB face side and ground.





- Is the voltage greater than 10 volts?

Yes
GO to AA4.

No
REPAIR circuit CLS30 (VT/WH) for an open. TEST the system for normal operation.

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AA4 CHECK FOR VOLTAGE TO THE TRAILER TOW PARKING LAMP RELAY

- Place the headlamp switch in the OFF position.
- Measure the voltage between the trailer tow parking lamp relay pin 3, circuit SBB08 (VT/RD), BJB face side and ground.





- Is the voltage greater than 10 volts?

Yes
GO to AA5.

No
VERIFY the BJB fuse 8 (20A) is OK. If OK, REPAIR circuit SBB08 (VT/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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AA5 CHECK FOR VOLTAGE TO THE TRAILER TOW PARKING LAMP RELAY COIL USING THE RELAY GROUND CIRCUIT

- Measure the voltage between the trailer tow parking lamp relay pin 3, circuit SBB08 (VT/RD), BJB face side and the trailer tow parking lamp relay pin 1, circuit GD120 (BK/GN), BJB face side.





- Is the voltage greater than 10 volts?

Yes
REPAIR circuit CAT11 (BN) for an open. TEST the system for normal operation.

No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.

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