Pinpoint Test Z: The Trailer Stop/Turn Lamp Is Inoperative
Trailer Lamps
Pinpoint Tests
Pinpoint Test Z: The Trailer Stop/Turn Lamp Is Inoperative
Refer to Wiring Diagram Set 95, Trailer/Camper Adapter for schematic and connector information. Diagrams By Number
Normal Operation
The Smart Junction Box (SJB) fuse 2 (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, the voltage is routed to the trailer tow LH stop/turn relay and 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, the voltage is routed to the trailer tow RH stop/turn relay and the trailer tow connector.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Trailer tow connector
- Trailer tow stop/turn relay
- Trailer
- SJB
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.
NOTE: Before beginning diagnostics, visually inspect the trailer tow connector mounted on the bumper for signs of corrosion or damage. Repair or install a new trailer tow connector as required.
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Z1 DETERMINE IF BOTH TRAILER STOP/TURN LAMPS ARE INOPERATIVE
- Ignition OFF.
- Determine if both trailer stop/turn lamps are inoperative.
- Are both trailer stop/turn lamps inoperative?
Yes
VERIFY the SJB fuse 2 (15A) is OK. If OK, GO to Z2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
No
GO to Z3.
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Z2 CHECK THE TRAILER TOW STOP/TURN RELAY VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- Disconnect: Trailer Tow LH Stop/Turn Relay.
- Disconnect: SJB C2280d.
- Measure the resistance between the trailer tow LH stop/turn relay pin 3, circuit SBP02 (YE/RD), BJB face side and the SJB C2280d-13, circuit SBP02 (YE/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to Z9.
No
REPAIR circuit SBP02 (YE/RD) for an open. Test the system for normal operation.
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Z3 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR
- Connect: SJB C2280d.
- For the LH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow connector LH stop/turn lamp voltage supply pins, circuit CAT06 (YE), component side and ground.
- For the RH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow connector RH stop/turn lamp voltage supply pins, circuit CAT09 (GN), component 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 Z4.
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Z4 CHECK THE TRAILER TOW STOP/TURN CIRCUIT FOR VOLTAGE
- Disconnect: Trailer Tow C4099.
- For the LH trailer stop/turn lamp, while applying the brake pedal, measure the voltage between the trailer tow C4099-1, 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 C4099-4, circuit CAT09 (GN), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new trailer tow connector. TEST the system for normal operation.
No
GO to Z5.
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Z5 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 C4099-1, 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 C4099-4, 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 Z6.
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Z6 CHECK FOR VOLTAGE TO THE TRAILER TOW STOP/TURN RELAY COIL
- For the trailer tow LH stop/turn relay, while applying the brake pedal, measure the voltage between the trailer tow LH stop/turn relay pin 1, circuit CLS18 (GY/BN), BJB face side and ground.
- For the trailer tow RH stop/turn relay, while applying the brake pedal, measure the voltage between the trailer tow RH stop/turn relay pin 1, circuit CLS19 (VT/OG), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to Z7.
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.
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Z7 CHECK FOR VOLTAGE TO THE TRAILER TOW STOP/TURN RELAY SWITCH
- For the trailer tow LH stop/turn relay, measure the voltage between the trailer tow LH stop/turn relay pin 3, circuit SBP02 (YE/RD), BJB face side and ground.
- For the trailer tow RH stop/turn relay, measure the voltage between the trailer tow RH stop/turn relay pin 3, circuit SBP02 (YE/RD), BJB face side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to Z8.
No
REPAIR circuit SBP02 (YE/RD) for an open. TEST the system for normal operation.
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Z8 CHECK THE TRAILER TOW STOP/TURN RELAY COIL GROUND CIRCUIT FOR AN OPEN
- Measure the voltage between the trailer tow LH stop/turn relay pin 3, circuit SBP02 (YE/RD), BJB face side and the trailer tow LH stop/turn relay pin 2, circuit GD120 (BK/GN), BJB face side.
- Measure the voltage between the trailer tow RH stop/turn relay pin 3, circuit SBP02 (YE/RD), BJB face side and the trailer tow RH stop/turn relay pin 2, circuit GD120 (BK/GN), BJB 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.
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Z9 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB 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 SJB. REFER to Body 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.
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