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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1681 (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 B1253

Pinpoint Test D: DTC B1251 Or B1253

WARNING: This page is about a different car, the 2010 Lincoln Town Car. 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
      • Fig 1: Measuring Resistance
      GF0018826Courtesy of FORD MOTOR CO.
    • Measure the resistance between the in-vehicle temperature sensor pins, component side.
    • Note the ambient temperature and compare the in-vehicle temperature sensor resistance with the table below.
      Temperature Resistance
      10-20°C (50-68°F) 37,000-58,000 ohms
      20-30°C (68-86°F) 24,000-37,000 ohms
      30-40°C (86-104°F) 16,000-24,000 ohms
    • Is the resistance within the specified values for the temperature range? 
    1. YES  : Go to  D2.
    2. NO  : INSTALL a new in-vehicle 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 on the HVAC module.
      • Fig 2: Measuring Voltage
      GF0047624Courtesy of FORD MOTOR CO.
    • Measure the voltage between in-vehicle temperature sensor C233-1, circuit 3058 (LG/RD), harness side and C233-2, circuit 3059 (YE/LG), harness side.
    • Is the voltage between 4.7 and 5.1 volts? 
    1. YES  : INSTALL a new in-vehicle temperature sensor. TEST the system for normal operation. If the code returns, INSTALL a new HVAC module. TEST the system for normal operation.
    2. NO  : If diagnosing DTC B1251  , go to  D3.

      If diagnosing DTC B1253  , go to  D5.

  3. D3 CHECK CIRCUIT 3058 (LG/RD) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: HVAC Module C228b
      • Fig 3: Measuring Resistance
      GF0047625Courtesy of FORD MOTOR CO.
    • Measure the resistance between HVAC module C228b-19, circuit 3058 (LG/RD), harness side and in-vehicle temperature sensor C233-1, circuit 3058 (LG/RD), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  D4.
    2. NO  : REPAIR circuit 3058 (LG/RD) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  4. D4 CHECK CIRCUIT 3059 (YE/LG) FOR AN OPEN 
      Fig 4: Measuring Resistance
      GF0047626Courtesy of FORD MOTOR CO.
    • Measure the resistance between HVAC module C228b-16, circuit 3059 (YE/LG), harness side and in-vehicle temperature sensor C233-2, circuit 3059 (YE/LG), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  D7.
    2. NO  : REPAIR circuit 3059 (YE/LG) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  5. D5 CHECK CIRCUIT 3058 (LG/RD) FOR A SHORT TO CIRCUIT 3059 (YE/LG) 
    • Key in OFF position.
    • Disconnect: HVAC Module C228b
      • Fig 5: Measuring Resistance
      GF0018830Courtesy of FORD MOTOR CO.
    • Measure the resistance between in-vehicle temperature sensor C233-1, circuit 3058 (LG/RD), harness side and C233-2, circuit 3059 (YE/LG), harness side.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  D6.
    2. NO  : REPAIR circuit 3058 (LG/RD) for a short to circuit 3059 (YE/LG). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  6. D6 CHECK CIRCUIT 3058 (LG/RD) FOR A SHORT TO GROUND 
      Fig 6: Measuring Resistance
      GF0047627Courtesy of FORD MOTOR CO.
    • Measure the resistance between HVAC module C228b-19, circuit 3058 (LG/RD), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  D7.
    2. NO  : REPAIR circuit 3058 (LG/RD) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  7. D7 CHECK HVAC MODULE CONNECTION 
    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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