Pinpoint Test J: The HVAC Module Does Not Respond To The Scan Tool

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 HVAC module communicates with the scan tool through the medium speed controller area network (MS-CAN). Circuits VDB06 (GY/OG) (MS-CAN +) and VDB07 (VT/OG) (MS-CAN -) provide the network connection to the HVAC module. The HVAC module shares the MS-CAN with the instrument cluster (IC), the accessory protocol interface module (APIM), the smart junction box (SJB), the audio control module (ACM), the audio digital signal processing (DSP) module (if equipped), the satellite digital audio receiver system (SDARS) module (if equipped), the rear entertainment module (RETM) (if equipped), the driver seat module (DSM) (if equipped), the parking aid module (PAM) (if equipped), the liftgate/trunk module (LTM) (if equipped) and the dual climate control seat module (DCSM) (if equipped). Voltage for the HVAC module is provided by circuits CBP37 (WH) and SBP15 (WH/RD). Circuit GD115 (BK/GY) provides ground.

This pinpoint test is intended to diagnose the following:

• Fuse
• Wiring, terminals or connectors
• HVAC module

PINPOINT TEST J: THE HVAC MODULE DOES NOT RESPOND TO THE SCAN TOOL 

1. J1 CHECK THE HVAC VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
   • Key in OFF position.
   • Disconnect: HVAC Module C228a
   • Key in ON position.
   Fig 1: Checking Circuits For Voltage
   Courtesy of FORD MOTOR CO.
   • Measure the voltage between the HVAC module C228a-13, circuit SBP15 (WH/RD), harness side and ground; and between the HVAC module C228a-12, circuit CBP37 (WH), harness side and ground.
   • Are the voltages greater than 10 volts? 
   1. YES  : Go to  J2.
   2. NO  : VERIFY the SJB fuse 15 (10A) or fuse 37 (10A) is OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
2. J2 CHECK THE HVAC GROUND CIRCUIT FOR AN OPEN 
   • Key in OFF position.
   Fig 2: Checking Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the HVAC module C228a-23, circuit GD115 (BK/GY), harness side and ground.
   • Is the resistance less than 5 ohms? 
   1. YES  : Go to  J3.
   2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. J3 CHECK THE MS-CAN CIRCUITS BETWEEN THE HVAC MODULE AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN 
   Fig 3: Checking MS-CAN Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the HVAC module C228a-25, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.
   Fig 4: Checking MS-CAN Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the HVAC module C228a-26, 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  J4.
   2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
4. J4 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.