Pinpoint Test AF: The Trailer Stop/Turn Lamp Is Inoperative

Trailer Lamps

Pinpoint Test AF: The Trailer Stop/Turn Lamp Is Inoperative

Normal Operation

The Battery Junction Box (BJB) fuse 63 (15A) supplies voltage to both trailer tow stop/turn relays.

The trailer tow LH stop/turn relay coil receives voltage when the vehicle LH rear stoplamp is illuminated. When the trailer tow LH stop/turn relay is energized, voltage is routed to the trailer tow connector.

The trailer tow RH stop/turn relay coil receives voltage when the vehicle RH rear stoplamp is illuminated. When the trailer tow RH stop/turn relay is energized, voltage is routed to the trailer tow connector.

This pinpoint test is intended to diagnose the following:

- Fuse

- Wiring, terminals or connectors

- Trailer tow stop/turn relay

- Trailer

PINPOINT TEST AF : THE TRAILER STOP/TURN 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.

AF1 DETERMINE IF BOTH TRAILER STOP/TURN LAMPS ARE INOPERATIVE

- Ignition OFF.

- For the LH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow C439-2, circuit CAT06 (YE), harness side and ground.






- For the RH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow C439-1, circuit CAT09 (GN), harness side and ground.






Are the voltages greater than 10 volts?

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

No
If no voltage is present at both pins, VERIFY the BJB (Battery Junction Box) fuse 63 (15A) is OK. If OK, REPAIR circuit SBB63 (WH/RD) for an open. TEST the system for normal operation. If not OK, REFER to Wiring Diagrams to identify the possible causes of the circuit short [1][2]Diagrams By Number.

If no voltage is present from at one pin, GO to AF2.

AF2 CHECK THE TRAILER TOW STOP/TURN RELAY

- Disconnect: Suspect Trailer Tow Stop/Turn Relay.

- Substitute a known good relay.

- For the LH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow C439-2, circuit CAT06 (YE), harness side and ground.






- For the RH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow C439-1, circuit CAT09 (GN), harness side and ground.






Is the voltage greater than 10 volts?

Yes
REMOVE the known good relay. INSTALL a new trailer tow stop/turn relay. TEST the system for normal operation.

No
REMOVE the known good relay. GO to AF3.

AF3 CHECK FOR VOLTAGE TO THE STOP/TURN LAMP RELAY COIL

- For the LH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow LH stop/turn relay pin 1, circuit CLS18 (GY/BN), BJB (Battery Junction Box) face side and ground.






- For the RH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow RH stop/turn relay pin 1, circuit CLS19 (VT/OG), BJB (Battery Junction Box) face side and ground.






Is the voltage greater than 10 volts?

Yes
GO to AF4.

No
REPAIR circuit CLS18 (GY/BN) (LH stop/turn) or circuit CLS19 (VT/OG) (RH stop/turn) for an open. TEST the system for normal operation.

AF4 CHECK FOR VOLTAGE TO THE STOP/TURN LAMP RELAY

- For the LH trailer stop/turn lamp, measure the voltage between the trailer tow LH stop/turn relay pin 3, circuit SBB63 (WH/RD), BJB (Battery Junction Box) face side and ground.






- For the RH trailer stop/turn lamp, measure the voltage between the trailer tow RH stop/turn relay pin 3, circuit SBB63 (WH/RD), BJB (Battery Junction Box) face side and ground.






Is the voltage greater than 10 volts?

Yes
GO to AF5.

No
REPAIR circuit SBB63 (WH/RD) for an open. TEST the system for normal operation.

AF5 CHECK THE STOP/TURN LAMP RELAY GROUND CIRCUIT FOR AN OPEN

- For the LH trailer stop/turn lamp, measure the voltage between the trailer tow LH stop/turn relay pin 3, circuit SBB63 (WH/RD), BJB (Battery Junction Box) face side and the trailer tow LH stop/turn relay pin 2, circuit GD120 (BK/GN), BJB (Battery Junction Box) face side.






- For the RH trailer stop/turn lamp, measure the voltage between the trailer tow RH stop/turn relay pin 3, circuit SBB63 (WH/RD), BJB (Battery Junction Box) face side and the trailer tow RH stop/turn relay pin 2, circuit GD120 (BK/GN), BJB (Battery Junction Box) face side.






Is the voltage greater than 10 volts?

Yes
REPAIR circuit CAT06 (YE) (LH trailer stop/turn) or circuit CAT09 (GN) (RH trailer stop/turn) for an open. TEST the system for normal operation.

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