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Pinpoint Test B: One Low Beam Headlamp Is Inoperative

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
  1. B1 CHECK CIRCUIT 57 (BK) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: Inoperative Headlamp
      • Fig 1: Checking Circuit For Open
      GF0014536Courtesy of FORD MOTOR CO.
    • Measure the resistance between the inoperative headlamp, harness side and ground as follows:
      Vehicle Inoperative Headlamp Connector-Pin Circuit
      Crown Victoria C1021-2 (LH)
      C1041-2 (RH)      		 57 (BK)
      Grand Marquis C1284-2 (LH)
      C1285-2 (RH)      		 57 (BK)
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  B2.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  2. B2 CHECK CIRCUIT 1055 (WH/LG) OR CIRCUIT 1056 (DB/LG) FOR AN OPEN 
    • Disconnect: LCM C2145d (LH Headlamp) or C2145c (RH Headlamp)
      • Fig 2: Checking Circuits For Open
      GF0014537Courtesy of FORD MOTOR CO.
    • Measure the voltage between the LCM C2145d-21 (LH low beam), circuit 1055 (WH/LG), harness side and ground; or between the LCM C2145c-19 (RH low beam), circuit 1056 (DB/LG), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  B3.
    2. NO  : VERIFY the CJB fuse 19 (10A) or fuse 21 (10A) is OK. If OK, REPAIR the circuit in question. TEST the system for normal operation.
  3. B3 CHECK THE HEADLAMP VOLTAGE SUPPLY CIRCUIT FOR AN OPEN OR SHORT TO GROUND 
    • Measure the resistance between the inoperative headlamp, harness side and the LCM, harness side; and between the inoperative headlamp, harness side and ground as follows:
      Vehicle Inoperative Headlamp Connector-Pin LCM Connector-Pin Circuit
      Crown Victoria C1021-1 (LH) C2145d-22 160 (DB/WH)
        C1041-1 (RH) C2145c-20 161 (DG/OG)
      Grand Marquis C1284-1 (LH) C2145c-22 160 (DB/WH)
        C1285-1 (RH) C2145c-20 161 (DG/OG)
    • Is the resistance less than 5 ohms between the headlamp and the LCM, and greater than 10,000 ohms between the headlamp and ground? 
    1. YES  : Go to  B4.
    2. NO  : REPAIR the circuit in question. TEST the system for normal operation.
  4. B4 CHECK FOR CORRECT LCM OPERATION 
    • Disconnect all the LCM connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the LCM 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 LCM. REFER to MULTIFUNCTION ELECTRONIC MODULES 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.
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