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Pinpoint Test C: DTC B1251 Or B1253

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.
  1. C1 CHECK THE SENSOR RESISTANCE 
    • Ignition OFF.
    • Disconnect: In-Vehicle Temperature Sensor C233.
    • Carry out the In-Vehicle Temperature Sensor component test. See Component Tests .
    • Does the in-vehicle temperature sensor test OK? 
    • Yes:  GO to C2  .
    • No:  INSTALL a new in-vehicle temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  2. C2 CHECK THE HVAC MODULE SENSOR OUTPUT VOLTAGE 
    • Ignition ON.
    • Press the AUTO button.
    • Measure the voltage between in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side and C233-1, circuit RH111 (GY/BU), harness side.
      Fig 1: Measuring Voltage Between In-Vehicle Temperature Sensor C233-2, Circuit VH414 (GN/BU) And C233-1, Circuit RH111 (GY/BU)
      G06505282Courtesy of FORD MOTOR CO.
    • Is the voltage between 4.7 and 5.1 volts? 
    • Yes:  INSTALL a new in-vehicle sensor. CLEAR the DTCs. REPEAT the self-test. If code returns, GO to  C7.
    • No: For DTC B1251  , GO to C3  .

      For DTC B1253  , GO to  C5.

  3. C3 CHECK CIRCUIT VH414 (GN/BU) FOR AN OPEN 
    • Ignition OFF.
    • Disconnect: HVAC Module - DATC  C228A.
    • Measure the resistance between HVAC module - DATC  C228A-3, circuit VH414 (GN/BU), harness side and in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side.
      Fig 2: Measuring Resistance Between DATC C228A-3, Circuit VH414 (GN/BU) And In-Vehicle Temperature Sensor C233-2, Circuit VH414 (GN/BU)
      G06505283Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes:  GO to C4  .
    • No:  REPAIR circuit VH414 (GN/BU) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  4. C4 CHECK CIRCUIT RH111 (GY/BU) FOR AN OPEN 
    • Measure the resistance between HVAC module - DATC  C228A-10, circuit RH111 (GY/BU), harness side and in-vehicle temperature sensor C233-1, circuit RH111 (GY/BU), harness side.
      Fig 3: Measuring Resistance Between DATC C228A-10, Circuit RH111 (GY/BU) And In-Vehicle Temperature Sensor C233-1, Circuit RH111 (GY/BU)
      G06505284Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes:  GO to  C7.
    • No:  REPAIR circuit RH111 (GY/BU) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  5. C5 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO CIRCUIT RH111 (GY/BU) 
    • Ignition OFF.
    • Disconnect: HVAC Module - DATC  C228A.
    • Measure the resistance between in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side and C233-1, circuit RH111 (GY/BU), harness side.
      Fig 4: Measuring Resistance Between In-Vehicle Temperature Sensor C233-2, Circuit VH414 (GN/BU) And C233-1, Circuit RH111 (GY/BU)
      G06505285Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 
    • Yes:  GO to C6  .
    • No:  REPAIR circuit VH414 (GN/BU) for a short to circuit RH111 (GY/BU). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  6. C6 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO GROUND 
    • Measure the resistance between HVAC module - DATC  C228A-3, circuit VH414 (GN/BU), harness side and ground.
      Fig 5: Measuring Resistance Between HVAC Module - DATC C228A-3, Circuit VH414 (GN/BU), Harness Side And Ground
      G06505286Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 
    • Yes:  GO to C7  .
    • No:  REPAIR circuit VH414 (GN/BU) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  7. C7 CHECK THE HVAC MODULE CONNECTION 
    • Inspect the HVAC module connectors for:
      • corrosion.
      • pushed-out terminals.
      • damaged terminals.
    • Connect and correctly seat all the HVAC module connectors.
    • Clear the DTCs.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    • Yes:  INSTALL a new HVAC module. REFER to CLIMATE CONTROL . 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 the DTCs. REPEAT the self-test. TEST the system for normal operation.
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