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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 E: DTC B1255 or B1257 >> Pinpoint Test E: DTC B1255 Or DTC B1257

Pinpoint Test E: DTC B1255 Or DTC B1257

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. E1 CHECK THE SENSOR RESISTANCE 
    • Key in OFF position.
    • Disconnect: Ambient Temperature Sensor C132
    • Carry out the Ambient Temperature Sensor .
    • Does the ambient temperature sensor test OK? 
    1. YES  : Go to  E2.
    2. NO  : INSTALL a new ambient temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  2. E2 CHECK THE HVAC MODULE OUTPUT VOLTAGE 
    • Key in ON position.
    • Press the AUTO button.
      • Fig 1: Checking EATC Sensor Output Voltage
      GF0030244Courtesy of FORD MOTOR CO.
    • Measure the voltage between ambient temperature sensor C132-A, circuit VH407 (YE/GN), harness side and C132-B, circuit RH104 (BU/BN), harness side.
    • Is the voltage between 4.7 and 5.1 volts? 
    1. YES  : INSTALL a new ambient sensor. CLEAR the DTCs. REPEAT the self-test. If code returns, go to  E7.
    2. NO  : If diagnosing DTC B1255  , go to  E3.

      If diagnosing DTC B1257  , go to  E5.

  3. E3 CHECK CIRCUIT VH407 (YE/GN) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: HVAC Module - DATC C2356b or HVAC Module - EATC C228b
      • Fig 2: Checking Circuit VH407 (YE/GN) For An Open (EATC)
      GF0041558Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-17, circuit VH407 (YE/GN), harness side and ambient temperature sensor C132-A, circuit VH407 (YE/GN), harness side.
      • Fig 3: Checking Circuit VH407 (YE/GN) For An Open (DATC)
      GF0041559Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-17, circuit VH407 (YE/GN), harness side and ambient temperature sensor C132-A, circuit VH407 (YE/GN), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  E4.
    2. NO  : REPAIR circuit VH407 (YE/GN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  4. E4 CHECK CIRCUIT RH104 (BU/BN) FOR AN OPEN 
      Fig 4: Checking Circuit RH104 (BU/BN) For An Open (EATC)
      GF0041560Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-3, circuit RH104 (BU/BN), harness side and ambient temperature sensor C132-B, circuit RH104 (BU/BN), harness side.
      • Fig 5: Checking Circuit RH104 (BU/BN) For An Open (DATC)
      GF0041561Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-3, circuit RH104 (BU/BN), harness side and ambient temperature sensor C132-B, circuit RH104 (BU/BN), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  E7.
    2. NO  : REPAIR circuit RH104 (BU/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  5. E5 CHECK CIRCUITS VH407 (YE/GN) 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 VH407 (YE/GN) For Short To Circuit RH104 (BU/BN)
      GF0030247Courtesy of FORD MOTOR CO.
    • Measure the resistance between ambient temperature sensor C132-A, circuit VH407 (YE/GN), harness side and C132-B, circuit RH104 (BU/BN), harness side.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  E6.
    2. NO  : REPAIR circuits VH407 (YE/GN) and RH104 (BU/BN) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  6. E6 CHECK CIRCUIT VH407 (YE/GN) FOR A SHORT TO GROUND 
      Fig 7: Checking Circuit VH407 (YE/GN) For A Short To Ground (EATC)
      GF0041562Courtesy of FORD MOTOR CO.
      NOTE: EATC systems only.
    • Measure the resistance between HVAC module - EATC C228b-17, circuit VH407 (YE/GN), harness side and ground.
      • Fig 8: Checking Circuit VH407 (YE/GN) For A Short To Ground (DATC)
      GF0017927Courtesy of FORD MOTOR CO.
      NOTE: DATC systems only.
    • Measure the resistance between HVAC module - DATC C2356b-17, circuit VH407 (YE/GN), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  E7.
    2. NO  : REPAIR circuit VH407 (YE/GN) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  7. E7 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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