Pinpoint Test V: Both Reversing 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.

V1 CHECK FOR VOLTAGE TO THE REVERSING LAMPS
- Ignition OFF.
- Disconnect: LH Reversing Lamp C451.
- Apply the parking brake.
- Ignition ON.
- Select REVERSE.
- Measure the voltage between the LH reversing lamp C451-2, circuit CBB07 (GN/BU), harness side and ground.
  
  Fig 1: Measuring Voltage Between LH Reversing Lamp C451-2, Circuit CBB07 (GN/BU), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: REPAIR circuit GD182 (BK/GY) for an open. TEST the system for normal operation.
- No: GO to V2 .
V2 CHECK THE REVERSING LAMPS RELAY
- Select PARK.
- Connect: LH Reversing Lamp C451.
- Disconnect: Reversing Lamps Relay.
- 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 FOR VOLTAGE TO THE REVERSING LAMPS RELAY
- Ignition ON.
- Measure the voltage between the reversing lamps relay pin 3, circuit CBB35 (YE/GY), BJB face side and ground.
  
  Fig 2: Measuring Voltage Between Reversing Lamps Relay Pin 3, Circuit CBB35 (YE/GY), BJB Face Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: GO to V4 .
- No: VERIFY the BJB fuse 35 (10A) is OK. If OK, REPAIR circuit CBB35 (YE/GY) 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.
V4 BYPASS THE REVERSING LAMPS RELAY
- Connect a fused jumper wire between the reversing lamps relay pin 3, circuit CBB35 (YE/GY), BJB face side and the reversing lamps relay pin 5, circuit CBB07 (GN/BU), BJB face side.
  
  Fig 3: Connecting Fused Jumper Wire Between Reversing Lamps Relay, BJB Face Side And Reversing Lamps Relay, BJB Face Side
  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 CBB07 (GN/BU) for an open. TEST the system for normal operation.
V5 CHECK FOR VOLTAGE TO THE REVERSING LAMPS RELAY COIL
- Measure the voltage between the reversing lamps relay pin 1, circuit CBK03 (GY) (non-hybrid) or circuit CBK02 (GN) (hybrid), BJB face side and ground.
  
  Fig 4: Checking Voltage To Reversing Lamps Relay Coil
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: GO to V6 .
- No: VERIFY the BJB fuse 27 (10A) (non-hybrid) or fuse 28 (15A) (hybrid) is OK. If OK, REPAIR circuit CBK03 (GY) (non-hybrid) or circuit CBK02 (GN) (hybrid) 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.
V6 CHECK FOR VOLTAGE TO THE PCM (AUTOMATIC TRANSAXLE) OR THE REVERSING LAMP SWITCH (MANUAL TRANSAXLE)
- Ignition OFF.
- Connect: Reversing Lamps Relay.
- Disconnect: Reversing Lamp Switch C169 (Manual Transaxle).
- Disconnect: PCM C175t (Automatic Transaxle).
- Ignition ON.
- For non-hybrid vehicles with an automatic transaxle, measure the voltage between the PCM C175t-33, circuit CLS28 (BU/WH), harness side and ground.
  
  Fig 5: Measuring Voltage Between PCM C175T-33, Circuit CLS28 (BU/WH), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- For hybrid vehicles with an automatic transaxle, measure the voltage between the PCM C175t-34, circuit CLS28 (BU/WH), harness side and ground.
  
  Fig 6: Measuring Voltage Between PCM C175T-34, Circuit CLS28 (BU/WH), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- For vehicles with a manual transaxle, measure the voltage between the reversing lamp switch C169-1, circuit CLS28 (BU/WH), harness side and ground.
  
  Fig 7: Measuring Voltage Between Reversing Lamp Switch C169-1, Circuit CLS28 (BU/WH), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: For vehicles with a manual transaxle, GO to V7 .
  For vehicles with an automatic transaxle, GO to V8.
- No: REPAIR circuit CLS28 (BU/WH) for an open. TEST the system for normal operation.
V7 CHECK FOR VOLTAGE TO THE REVERSING LAMP SWITCH USING THE CONNECTOR GROUND
- Measure the voltage between the reversing lamp switch C169-1, circuit CLS28 (BU/WH), harness side and the reversing lamp switch C169-2, circuit GD120 (BK/GN), harness side.
  
  Fig 8: Checking Voltage To Reversing Lamp Switch Using Connector Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes: INSTALL a new reversing lamp switch. REFER to REVERSING LAMP SWITCH . TEST the system for normal operation.
- No: REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
V8 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 - 2.5L , ELECTRONIC ENGINE CONTROLS - 3.0L (4V) or ELECTRONIC ENGINE CONTROLS - HYBRID . 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.