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Home >> Ford >> 2012 >> Mustang Base, 2D Coupe, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 243 (Exterior Lighting System) >> Diagnosis And Testing >> Trailer Lamps >> Pinpoint Tests >> Pinpoint Test Y: The Trailer Stop/Turn Lamp Is Inoperative >> Pinpoint Test Y: The Trailer Stop/Turn Lamp Is Inoperative

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

WARNING: This page is about a different car, the 2013 Ford F-150. 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.
NOTE: Before beginning diagnostics, visually inspect the trailer tow connector for signs of corrosion or damage. Repair or install a new trailer tow connector as required.
  1. Y1 VERIFY THE TRAILER LAMP OPERATION 
    • Ignition OFF.
    • Determine if both trailer stop/turn lamps are inoperative.
    • Are both trailer stop/turn lamps inoperative? 
    • Yes  : VERIFY the BJB fuse 73 (20A) is OK. If OK, REPAIR circuit SBB73 (RD) for an open. TEST the system for normal operation.
    • No  : For an inoperative LH trailer lamp, GO to Y2.

      For an inoperative RH trailer lamp, GO to  Y8.

  2. Y2 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR (LH TRAILER STOP/TURN LAMP) 
    • For the 4-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439B-2, circuit CAT06 (YE), harness side and ground.
      Fig 1: Measuring Voltage Between Trailer Tow C439B-2, Circuit CAT06 (YE) And Ground
      G06099227Courtesy of FORD MOTOR CO.
    • For the 7-pin connector, while applying the brake pedal, measure the voltage between the trailer tow connector pin 1, circuit CAT06 (YE), component side and ground.
      Fig 2: Measuring Voltage Between Trailer Tow Connector Pin 1, Circuit CAT06 (YE), Component Side And Ground
      G06133848Courtesy 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  : For the 4-pin connector, GO to  Y4.

      For the 7-pin connector, GO to Y3.

  3. Y3 CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR (LH STOP/TURN 7-PIN) 
    • Disconnect: Trailer Tow C439A.
    • While applying the brake pedal, measure the voltage between the trailer tow C439A-1, circuit CAT06 (YE), harness side and ground.
      Fig 3: Measuring Voltage Between Trailer Tow C4099-1, Circuit CAT06 (YE), Harness Side And Ground
      G06065321Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : INSTALL a new trailer tow connector. TEST the system for normal operation.
    • No  : GO to Y4.
  4. Y4 CHECK THE TRAILER TOW LH STOP/TURN RELAY 
    • Disconnect: Trailer Tow LH Stop/Turn Relay.
    • Substitute a known good relay.
    • For the 4-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439B-2, circuit CAT06 (YE), harness side and ground.
      Fig 4: Measuring Voltage Between Trailer Tow C439B-2, Circuit CAT06 (YE), Harness Side And Ground
      G06099227Courtesy of FORD MOTOR CO.
    • For the 7-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439A-1, circuit CAT06 (YE), harness side and ground.
      Fig 5: Measuring Voltage Between Trailer Tow C439A-1, Circuit CAT06 (YE) And Ground
      G06065321Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : REMOVE the known good relay. INSTALL a new trailer tow turn relay. TEST the system for normal operation.
    • No  : REMOVE the known good relay. GO to Y5.
  5. Y5 CHECK FOR VOLTAGE TO THE LH STOP/TURN LAMP RELAY COIL 
    • While applying the brake pedal, measure the voltage between the trailer tow LH turn relay pin 1, circuit CLS18 (GY/BN), BJB face side and ground.
      Fig 6: Measuring Voltage Between Trailer Tow LH Turn Relay Pin 1, Circuit CLS18 (GY/BN), BJB Face Side And Ground
      G06143944Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to Y6.
    • No  : REPAIR circuit CLS18 (GY/BN) for an open. TEST the system for normal operation.
  6. Y6 CHECK THE VOLTAGE SUPPLY CIRCUIT TO THE LH STOP/TURN LAMP RELAY 
    • Measure the voltage between the trailer tow LH turn relay pin 3, circuit SBB73 (RD), BJB face side and ground.
      Fig 7: Measuring Voltage Between Trailer Tow LH Turn Relay Pin 3, Circuit SBB73 (RD), BJB Face Side And Ground
      G06133853Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to Y7.
    • No  : REPAIR circuit SBB73 (RD) for an open. TEST the system for normal operation.
  7. Y7 CHECK THE LH STOP/TURN LAMP RELAY GROUND CIRCUIT FOR AN OPEN 
    • Measure the voltage between the trailer tow LH turn relay pin 3, circuit SBB73 (RD), BJB face side and the trailer tow LH turn relay pin 2, circuit GD123 (BK/GY), BJB face side.
      Fig 8: Measuring Voltage Between Trailer Tow LH Turn Relay Pin 3, Circuit SBB73 (RD), BJB Face Side And Relay Pin 2, Circuit GD123 (BK/GY), BJB Face Side
      G06133854Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : REPAIR circuit CAT06 (YE) for an open. TEST the system for normal operation.
    • No  : REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
  8. Y8 CHECK FOR VOLTAGE THROUGH THE TRAILER TOW CONNECTOR (RH TRAILER STOP/TURN LAMP) 
    • For the 4-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439B-1, circuit CAT09 (GN), harness side and ground.
      Fig 9: Measuring Voltage Between Trailer Tow C439B-1, Circuit CAT09 (GN) And Ground
      G06099228Courtesy of FORD MOTOR CO.
    • For the 7-pin connector, while applying the brake pedal, measure the voltage between the trailer tow connector pin 4, circuit CAT09 (GN), component side and ground.
      Fig 10: Measuring Voltage Between Trailer Tow Connector Pin 4, Circuit CAT09 (GN) And Ground
      G06133856Courtesy 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  : For the 4-pin connector, GO to  Y10.

      For the 7-pin connector, GO to Y9.

  9. Y9 CHECK FOR VOLTAGE TO THE TRAILER TOW CONNECTOR (RH STOP/TURN 7-PIN) 
    • Disconnect: Trailer Tow C439A.
    • While applying the brake pedal, measure the voltage between the trailer tow C439A-4, circuit CAT09 (GN), harness side and ground.
      Fig 11: Measuring Voltage Between Trailer Tow C439A-4, Circuit CAT09 (GN) And Ground
      G06065322Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : INSTALL a new trailer tow connector. TEST the system for normal operation.
    • No  : GO to Y10.
  10. Y10 CHECK THE TRAILER TOW RH STOP/TURN RELAY 
    • Disconnect: Trailer Tow RH Stop/Turn Relay.
    • Substitute a known good relay.
    • For the 4-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439B-1, circuit CAT09 (GN), harness side and ground.
      Fig 12: Measuring Voltage Between Trailer Tow C439B-1, Circuit CAT09 (GN) And Ground
      G06099228Courtesy of FORD MOTOR CO.
    • For the 7-pin connector, while applying the brake pedal, measure the voltage between the trailer tow C439A-4, circuit CAT09 (GN), harness side and ground.
      Fig 13: Measuring Voltage Between Trailer Tow C439A-4, Circuit CAT09 (GN) And Ground
      G06065322Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : REMOVE the known good relay. INSTALL a new trailer tow turn relay. TEST the system for normal operation.
    • No  : REMOVE the known good relay. GO to Y11.
  11. Y11 CHECK FOR VOLTAGE TO THE RH STOP/TURN LAMP RELAY COIL 
    • While applying the brake pedal, measure the voltage between the trailer tow RH turn relay pin 1, circuit CLS19 (VT/OG), BJB face side and ground.
      Fig 14: Measuring Voltage Between Trailer Tow RH Turn Relay Pin 1, Circuit CLS19 (VT/OG), BJB Face Side And Ground
      G06133860Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to Y12.
    • No  : REPAIR circuit CLS19 (VT/OG) for an open. TEST the system for normal operation.
  12. Y12 CHECK THE VOLTAGE SUPPLY CIRCUIT TO THE RH STOP/TURN LAMP RELAY 
    • Measure the voltage between the trailer tow RH turn relay pin 3, circuit SBB73 (RD), BJB face side and ground.
      Fig 15: Measuring Voltage Between Trailer Tow RH Turn Relay Pin 3, Circuit SBB73 (RD), BJB Face Side And Ground
      G06133861Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to Y13.
    • No  : REPAIR circuit SBB73 (RD) for an open. TEST the system for normal operation.
  13. Y13 CHECK THE RH STOP/TURN LAMP RELAY GROUND CIRCUIT FOR AN OPEN 
    • Measure the voltage between the trailer tow RH turn relay pin 3, circuit SBB73 (RD), BJB face side and the trailer tow RH turn relay pin 2, circuit GD123 (BK/GY), BJB face side.
      Fig 16: Measuring Voltage Between Trailer Tow RH Turn Relay Pin 3, Circuit SBB73 (RD), BJB Face Side And Turn Relay Pin 2, Circuit GD123 (BK/GY), BJB Face Side
      G06133862Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : REPAIR circuit CAT09 (GN) for an open. TEST the system for normal operation.
    • No  : REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
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