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Pinpoint Test I: The Heating Ventilation Air Conditioning (HVAC) Module Does Not Respond To The Scan Tool

WARNING: This page is about a different car, the 2008 Mercury Milan, 2008 Lincoln MKZ, and 2008 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. I1 CHECK THE HVAC VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: HVAC Module C228a (Single-Zone) or C2356a (Dual-Zone)
    • Key in ON position.
    • Measure the voltage between the HVAC module C228a-26 (single-zone) or HVAC module C2356a-26 (dual-zone), circuit SBP07 (WH/RD) circuit CBP20 (YE/VT), harness side and ground.
      • Fig 1: Checking HVAC Voltage Supply Circuits For An Open
      GF0030558Courtesy of FORD MOTOR CO.
    • Measure the voltage between the HVAC module C228a-19 (single-zone) or HVAC module C2356a-19 (dual-zone), circuit CBP20 (YE/VT), harness side and ground.
    • Are the voltages greater than 10 volts? 
    1. YES  : Go to  I2.
    2. NO  : VERIFY smart junction box (SJB) fuses 13 (10A) or 27 (7.5A) are OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  2. I2 CHECK THE HVAC GROUND CIRCUIT FOR AN OPEN 
    • Key in OFF position.
      • Fig 2: Checking HVAC Ground Circuit For An Open
      GF0030559Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-1 (single-zone) or C2356a-1 (dual-zone), circuit GD116 (BK/VT) and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  I3.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
  3. I3 CHECK THE MS-CAN CIRCUITS BETWEEN THE DATA LINK CONNECTOR (DLC) AND THE HVAC MODULE FOR AN OPEN 
      Fig 3: Checking Medium Speed CAN Circuits Between DLC And EATC Module Or DATC Module For Open (1 Of 2)
      GF0030560Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-12 (single-zone) or C2356a-12 (dual-zone), circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.
      • Fig 4: Checking Medium Speed CAN Circuits Between DLC And EATC Module Or DATC Module For Open (2 Of 2)
      GF0030561Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-13 (single-zone) or C2356a-13 (dual-zone), circuit VDB07 (VT/OG), harness side and the DLC C251-11, circuit VDB07 (VT/OG), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  I4.
    2. NO  : REPAIR the circuit as necessary. CLEAR the DTCs. REPEAT the network test with the scan tool.
  4. I4 CHECK FOR CORRECT HVAC MODULE OPERATION 
    • Disconnect all the HVAC module connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the HVAC module 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 HVAC module. REFER to CLIMATE CONTROL article. CLEAR the DTCs. REPEAT the network test with the scan tool.
    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 network test with the scan tool.
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