Pinpoint Test V: The Reversing Lamps Are Inoperative

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.

V1 CHECK FOR PCM TR SENSOR DTCs FROM THE SELF-TEST
- Review the DTCs from the PCM Key ON Engine OFF (KOEO) self-test.
- Are any Transmission Range (TR) sensor DTCs present?
- Yes: REFER to DIAGNOSIS AND TESTING .
- No: VERIFY the BJB fuse 44 (10A) is OK. If OK, GO to V2 . 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.
V2 CHECK THE REVERSING LAMPS RELAY
- Ignition OFF.
- Disconnect: Reversing Lamps Relay.
- Ignition ON.
- Substitute a known good relay and recheck the reversing lamps operation.
- Do the reversing lamps operate correctly?
- Yes: REMOVE the known good relay. INSTALL a new reversing lamps relay. TEST the system for normal operation.
- No: REMOVE the known good relay. GO to V3 .
V3 CHECK THE BJB
- Measure the voltage between the reversing lamps relay pin 5, BJB face side and ground; and between the reversing lamps relay pin 1, BJB face side and ground.
  
  Fig 1: Measuring Voltage Between Reversing Lamps Relay Pin 5 BJB Face Side And Ground
  Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
- Yes: GO to V4 .
- No: INSTALL a new BJB . TEST the system for normal operation.
V4 BYPASS THE REVERSING LAMPS RELAY
- Connect a fused jumper wire between the reversing lamps relay pin 5, BJB face side and the reversing lamps relay pin 3, circuit CLS10 (GN/BN), BJB face side.
  
  Fig 2: Connecting Fused Jumper Wire Between Reversing Lamps Relay Pin 5 And Reversing Lamps Relay Pin 3, Circuit CLS10 (GN/BN)
  Courtesy of FORD MOTOR CO.
- Do the reversing lamps illuminate?
- Yes: REMOVE the jumper wire. GO to V5 .
- No: REMOVE the jumper wire. REPAIR circuit CLS10 (GN/BN) for an open. TEST the system for normal operation.
V5 CHECK THE REVERSING LAMPS RELAY COIL GROUND CONTROLLED CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: PCM C175t.
- Ignition ON.
- Measure the voltage between the reversing lamps relay pin 2, circuit CLS28 (BU/WH), BJB face side and ground.
  
  Fig 3: Measuring Voltage Between Reversing Lamps Relay Pin 2, Circuit CLS28 (BU/WH) BJB Face Side And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes: REPAIR circuit CLS28 (BU/WH) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
- No: GO to V6 .
V6 CHECK FOR VOLTAGE TO THE PCM
- Ignition OFF.
- Connect: Reversing Lamps Relay.
- Measure the voltage between the PCM C175t-3, circuit CLS28 (BU/WH), harness side and ground.
  
  Fig 4: Measuring Voltage Between PCM C175T-3, Circuit CLS28 (BU/WH) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: GO to V7 .
- No: REPAIR circuit CLS28 (BU/WH) for an open. CLEAR the DTCs. REPEAT the self-test.
V7 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
  - corrosion
  - damaged pins
  - pushed-out pins
- Connect all the PCM 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 PCM. REFER to ELECTRONIC ENGINE CONTROLS . 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. CLEAR any DTCs. REPEAT the self-test.