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

Trailer Lamps

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

Refer to Wiring Diagram Set 95, Trailer/Camper Adapter for schematic and connector information Electrical Diagrams.

Normal Operation

The Battery Junction Box (BJB) fuse 14 (15A) supplies voltage to the LH and RH 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 Z : 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.

Z1 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR

- Ignition OFF.

- Disconnect: Trailer Tow C439.

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

No
GO to Z2.

Z2 CHECK THE TRAILER TOW STOP/TURN RELAY

- Disconnect: Suspect Trailer Tow Stop/Turn Relay.

- Substitute a know 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 Z3.

Z3 CHECK FOR VOLTAGE TO THE TRAILER TOW STOP/TURN RELAY COIL

- While applying the brake pedal, measure the voltage between the trailer tow LH stop/turn relay pin 2, circuit CLS18 (GY/BN), BJB (Battery Junction Box) face side and ground; or between the trailer tow RH stop/turn relay pin 2, circuit CLS19 (VT/OG), BJB (Battery Junction Box) face side and ground.





Is the voltage greater than 10 volts?

Yes
GO to Z4.

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

Z4 CHECK FOR VOLTAGE TO THE TRAILER TOW STOP/TURN RELAY

- Measure the voltage between the trailer tow LH stop/turn relay pin 3, circuit SBB14 (BN/RD), BJB (Battery Junction Box) face side and ground; or between the trailer tow RH stop/turn relay pin 3, circuit SBB14 (BN/RD), BJB (Battery Junction Box) face side and ground.





Is the voltage greater than 10 volts?

Yes
GO to Z5.

No
VERIFY the BJB (Battery Junction Box) fuse 14 (15A) is OK. If OK, REPAIR circuit SBB14 (BN/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 Electrical Diagrams.

Z5 CHECK FOR VOLTAGE TO THE TRAILER TOW STOP/TURN RELAY USING THE RELAY GROUND

- For the LH trailer stop/turn lamp, measure the voltage between the trailer tow LH turn relay pin 3, circuit SBB14 (BN/RD), BJB (Battery Junction Box) face side and the trailer tow LH turn relay pin 1, circuit GD120 (BK/GN), BJB (Battery Junction Box) face side.





- For the RH trailer stop/turn lamp, measure the voltage between the trailer tow LH turn relay pin 3, circuit SBB14 (BN/RD), BJB (Battery Junction Box) face side and the trailer tow LH turn relay pin 1, 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.