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Home >> Mercury >> 2010 >> Milan Base, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 818 (Exterior Lighting System (F250-F550)) >> Diagnostic Tests >> Reversing Lamps >> Pinpoint Tests >> Pinpoint Test U: The Reversing Lamps Are Inoperative >> Pinpoint Test U: The Reversing Lamps Are Inoperative

Pinpoint Test U: The Reversing Lamps Are Inoperative

WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.
  1. U1 CHECK THE REVERSING LAMP RELAY 
    • Key in OFF position.
    • Disconnect: Reversing Lamp Relay C2257
    • Carry out the reversing lamp relay component test. Refer to COMPONENT TESTING article.
    • Is the reversing lamp relay OK? 
    1. YES  : Go to  U2.
    2. NO  : INSTALL a new reversing lamp relay. TEST the system for normal operation.
  2. U2 CHECK THE REVERSING LAMP RELAY OUTPUT CIRCUITRY 
      Fig 1: Connecting Fused Jumper Wire
      G03879653Courtesy of FORD MOTOR CO.
    • Connect a fused (15A) jumper wire between the reversing lamp relay C2257-3, harness side and the reversing lamp relay C2257-5, circuit 140 (BK/PK), harness side.
    • Are the reversing lamps illuminated? 
    1. YES  : REMOVE the jumper wire. Go to  U4 .
    2. NO  : REMOVE the jumper wire. VERIFY the CJB fuse 8 (15A) is OK. If OK, go to  U3 .
  3. U3 CHECK CIRCUIT 140 (BK/PK) FOR AN OPEN 
    • Disconnect: CJB C270g
      • Fig 2: Checking Circuit For Open
      GF0008330Courtesy of FORD MOTOR CO.
    • Measure the resistance between the CJB C270g-1, circuit 140 (BK/PK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new CJB. TEST the system for normal operation.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  4. U4 CHECK THE CJB 
    • Key in ON position.
      • Fig 3: Checking Circuit For Voltage
      GF0008331Courtesy of FORD MOTOR CO.
    • Measure the voltage between the reversing lamp relay C2257-1, harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  U5.
    2. NO  : INSTALL a new CJB. TEST the system for normal operation.
  5. U5 CHECK THE REVERSING LAMP RELAY CONTROL CIRCUIT 
    • Key in OFF position.
    • Connect: Reversing Lamp Relay C2257
    • Disconnect: PCM C175b or C1381b (Automatic Transmission)
    • Disconnect: Reversing Lamp Switch C169 (Manual Transmission)
    • Key in ON position.
    • Measure the voltage between the PCM or reversing lamp switch, harness side and ground as follows:
      Vehicle Equipment Component Connector-Pin Circuit
      Automatic transmission with diesel engine PCM C1381b-3 324 (YE/LG)
      Automatic transmission with gasoline engine PCM C175b-24 324 (YE/LG)
      Manual transmission Reversing lamp switch C169-1 324 (YE/LG)
    • Is the voltage greater than 10 volts? 
    1. YES  : If equipped with a manual transmission, go to  U7 .

      If equipped with an automatic transmission, go to  U8 .

    2. NO  : Go to  U6.
  6. U6 CHECK CIRCUIT 324 (YE/LG) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: CJB C270f
    • Measure the resistance between the PCM or reversing lamp switch, harness side and the CJB, harness side as follows:
      Vehicle Equipment Component Connector-Pin CJB Connector-Pin Circuit
      Automatic transmission with diesel engine PCM C1381b-3 CJB C270f-8 324 (YE/LG)
      Automatic transmission with gasoline engine PCM C175b-24 CJB C270f-8 324 (YE/LG)
      Manual transmission Reversing lamp switch C169-1 CJB C270f-8 324 (YE/LG)
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new CJB. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  7. U7 CHECK CIRCUIT 57 (BK) FOR AN OPEN 
    • Key in OFF position.
      • Fig 4: Checking Circuit For Open
      GF0008332Courtesy of FORD MOTOR CO.
    • Measure the resistance between the reversing lamp switch C169-2, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new reversing lamp switch. TEST the system for normal operation.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  8. U8 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Check for:
      • corrosion
      • 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? 
    1. YES  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS - GASOLINE ENGINES article or ELECTRONIC ENGINE CONTROLS - DIESEL ENGINE article. TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
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