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Home >> Mercury >> 2008 >> Milan Base, 2.3 Z, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 1354 (HVAC Climate Control System - General Information And Diagnostics) >> Diagnostic Tests >> Climate Control System >> Pinpoint Tests >> Pinpoint Test D: DTC B1251 or B1253 >> Pinpoint Test D: DTC B1251 Or DTC B1253

Pinpoint Test D: DTC B1251 Or DTC B1253

WARNING: This page is about a different car, the 2009 Mercury Milan, 2009 Lincoln MKZ, and 2009 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
  1. D1 CHECK THE SENSOR RESISTANCE 
    • Key in OFF position.
    • Disconnect: In-Vehicle Temperature Sensor C233
    • Carry out the In-Vehicle Temperature Sensor .
    • Does the in-vehicle temperature sensor test OK? 
    1. YES  : Go to  D2.
    2. NO  : INSTALL a new in-car temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  2. D2 CHECK THE HVAC MODULE OUTPUT VOLTAGE 
    • Key in ON position.
    • Press the AUTO button.
      • Fig 1: Checking EATC Sensor Output Voltage
      GF0030240Courtesy of FORD MOTOR CO.
    • Measure the voltage between in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side and C233-1, circuit RH104 (BU/BN), harness side.
    • Is the voltage between 4.7 and 5.1 volts? 
    1. YES  : INSTALL a new in-vehicle sensor. CLEAR the DTCs. REPEAT the self-test. If code returns, go to  D7.
    2. NO  : If diagnosing DTC B1251  , go to  D3.

      If diagnosing DTC B1253  , go to  D5.

  3. D3 CHECK CIRCUIT VH414 (GN/BU) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: HVAC Module - DATC C2356b or HVAC Module - EATC C228b
      • Fig 2: Checking Circuit VH414 (GN/BU) For An Open (EATC)
      GF0041553Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-4, circuit VH414 (GN/BU), harness side and in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side.
      • Fig 3: Checking Circuit VH414 (GN/BU) For An Open (DATC)
      GF0041554Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-4, circuit VH414 (GN/BU), harness side and in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  D4.
    2. NO  : REPAIR circuit VH414 (GN/BU) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  4. D4 CHECK CIRCUIT RH104 (BU/BN) FOR AN OPEN 
      Fig 4: Checking Circuit RH104 (BU/BN) For An Open (EATC)
      GF0041555Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-3, circuit RH104 (BU/BN), harness side and in-vehicle temperature sensor C233-1, circuit RH104 (BU/BN), harness side.
      • Fig 5: Checking Circuit RH104 (BU/BN) For An Open (DATC)
      GF0041556Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-3, circuit RH104 (BU/BN), harness side and in-vehicle temperature sensor C233-1, circuit RH104 (BU/BN), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  D7.
    2. NO  : REPAIR circuit RH104 (BU/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  5. D5 CHECK CIRCUITS VH414 (GN/BU) AND RH104 (BU/BN) FOR A SHORT TOGETHER 
    • Key in OFF position.
    • Disconnect: HVAC Module - DATC C2356b or HVAC Module - EATC C228b
      • Fig 6: Checking Circuit VH414 (GN/BU) For Short To Circuit RH104 (BU/BN)
      GF0030243Courtesy of FORD MOTOR CO.
    • Measure the resistance between in-vehicle temperature sensor C233-2, circuit VH414 (GN/BU), harness side and C233-1, circuit RH104 (BU/BN), harness side.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  D6.
    2. NO  : REPAIR circuits VH414 (GN/BU) and RH104 (BU/BN) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  6. D6 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO GROUND 
      Fig 7: Checking Circuit VH414 (GN/BU) For A Short To Ground (EATC)
      GF0041557Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-4, circuit VH414 (GN/BU), harness side and ground.
      • Fig 8: Checking Circuit VH414 (GN/BU) For A Short To Ground (DATC)
      GF0017924Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-4, circuit VH414 (GN/BU), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  D7.
    2. 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. D7 CHECK THE MODULE CONNECTION 
    • Carry out the HVAC Module Cold Boot Process.
    • Carry out the HVAC Module - Electronic Automatic Temperature Control (EATC) and HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self Test.
    • Operate the system.
    • Does the concern return? 
    1. YES  : INSTALL a new HVAC module. REFER to CLIMATE CONTROL 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. TEST the system for normal operation.
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