Pinpoint Test Aa: The Trailer Parking Lamps Are Inoperative - Trailer Parking Lamps

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. 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.
- 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.
  
  Fig 1: Measuring Voltage Between Trailer Tow C439-3, Circuit CAT11 (BN) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.
- No: VERIFY the BJB fuse 9 (20A) is OK. If OK, GO to AA2 . If not OK, REFER to the SYSTEM WIRING DIAGRAMS for Edge or SYSTEM WIRING DIAGRAMS for MKX to identify the possible causes of the circuit short.
AA2 CHECK THE TRAILER TOW PARKING LAMP RELAY
- Place the headlamp switch in the OFF position.
- Disconnect: Trailer Tow Parking Lamp Relay.
- Substitute a known good relay.
- 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.
  
  Fig 2: Measuring Voltage Between Trailer Tow C439-3, Circuit CAT11 (BN) And Ground
  Courtesy of FORD MOTOR CO.
- 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 PARKING LAMP RELAY COIL
- Measure the voltage between the trailer tow parking lamp relay pin 1, circuit CLS30 (VT/WH), BJB face side and ground.
  
  Fig 3: Measuring Voltage Between Trailer Tow Parking Lamp Relay Pin 1, Circuit CLS30 (VT/WH) BJB Face Side And Ground
  Courtesy of FORD MOTOR CO.
- 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 THE BJB
- Place the headlamp switch in the OFF position.
- Measure the voltage between the trailer tow parking lamp relay pin 5, BJB face side and ground.
  
  Fig 4: Measuring Voltage Between Trailer Tow Parking Lamp Relay Pin 5 BJB Face Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: GO to AA5 .
- No: VERIFY the BJB fuse 9 (20A) is OK. If OK, INSTALL a new BJB . TEST the system for normal operation. If not OK, REFER to the SYSTEM WIRING DIAGRAMS for Edge or SYSTEM WIRING DIAGRAMS for MKX to identify the possible causes of the circuit short.
AA5 CHECK FOR VOLTAGE TO THE PARKING LAMP RELAY USING THE RELAY GROUND PIN
- Measure the voltage between the trailer tow parking lamp relay pin 5, BJB face side and the trailer tow parking lamp relay pin 2, circuit GD120 (BK/GN), BJB face side.
  
  Fig 5: Measuring Voltage Between Trailer Tow Parking Lamp Relay Pin 5, BJB Face Side And Pin 2, Circuit GD120 (BK/GN) BJB Face Side
  Courtesy of FORD MOTOR CO.
- 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.