Pinpoint Test Aa: The Trailer Parking Lamps Are Inoperative
WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
- 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 .
- 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 .
- 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.
- 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 appropriate SYSTEM WIRING DIAGRAMS article to identify the possible causes of the circuit short.
- 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.