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

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Module Communications Network for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Automatic Climate Control System for schematic and connector information.

Normal Operation 

The heating ventilation air conditioning (HVAC) module (if equipped) communicates with the scan tool through the standard corporate protocol (SCP) communication network. Circuits 914 (TN/OG) (SCP +) and 915 (PK/LB) (SCP-) provide the network connection to the HVAC module. The HVAC module shares the SCP network with the lighting control module (LCM), the driver door module (DDM) (if equipped), the overhead console message center (MC) (if equipped) and the instrument cluster (IC). Voltage for the HVAC module is provided by circuits 1812 (BN/WH) and 1566 (RD/YE). Circuit 57 (BK) provides ground.

This pinpoint test is intended to diagnose the following:

PINPOINT TEST E: THE HEATING VENTILATION AIR CONDITIONING (HVAC) MODULE DOES NOT RESPOND TO THE SCAN TOOL 

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. E1 CHECK THE HVAC MODULE VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: HVAC Module C228a
    • Key in ON position.
      • Fig 1: Checking Circuit For Voltage
      GF0014640Courtesy of FORD MOTOR CO.
    • Measure the voltage between the HVAC module C228a-2, circuit 1566 (RD/YE) harness side and ground.
      • Fig 2: Checking Circuit For Voltage
      GF0014641Courtesy of FORD MOTOR CO.
    • Measure the voltage between the HVAC module C228a-16, circuit 1812 (BN/WH) harness side and ground.
    • Are the voltages greater than 10 volts? 
    1. YES  : Go to  E2.
    2. NO  : VERIFY the central junction box (CJB) fuses 8 (10A) and 15 (10A) are OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
  2. E2 CHECK THE HVAC MODULE GROUND CIRCUITS FOR AN OPEN 
    • Key in OFF position.
      • Fig 3: Checking Circuit For Open
      GF0014642Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-3, circuit 57 (BK) harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  E3.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
  3. E3 CHECK THE SCP CIRCUITS BETWEEN THE DATA LINK CONNECTOR (DLC) AND THE HVAC MODULE FOR AN OPEN 
      Fig 4: Checking Circuit For Open
      GF0014643Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-15, circuit 914 (TN/OG), harness side and the DLC C251-2, circuit 914 (TN/OG), harness side.
      • Fig 5: Checking Circuit For Open
      GF0014644Courtesy of FORD MOTOR CO.
    • Measure the resistance between the HVAC module C228a-1, circuit 915 (PK/LB), harness side and the DLC C251-10, circuit 915 (PK/LB), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  E4.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  4. E4 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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