Pinpoint Test G: No Communication With The Dual/Electronic Automatic Temperature Control Module

WARNING: This page is about a different car, the 2005 Lincoln Navigator and 2005 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

G1 CHECK CIRCUIT 875 (BK/LB) FOR AN OPEN
- Key in OFF position.
- Disconnect: DATC Module C228a.
- Measure the resistance between the DATC module C228a-2, circuit 875 (BK/LB) and ground.
  
  Fig 1: Measuring Resistance Between Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 25 ohms?
- Yes : GO to G2.
- No : REPAIR circuit 875 (BK/LB) for an open. TEST the system for normal operation.
G2 CHECK CIRCUIT 729 (RD/WH) FOR B+
- Disconnect: DATC module C228b.
- Measure the voltage between the DATC module C228a-3, circuit 729 (RD/WH) and ground.
  
  Fig 2: Checking Circuit 729 (RD/WH) For B+
  Courtesy of FORD MOTOR CO.
- Is the voltage B+?
- Yes : GO to G3.
- No : REPAIR circuit 729 (RD/WH) for an open. TEST the system for normal operation.
G3 CHECK CIRCUIT 296 (WH/VT) FOR B+
- Key in ON position.
- Measure the voltage between the DATC module C228a-16, circuit 296 (WH/VT) and ground.
  
  Fig 3: Checking Circuit 296 (WH/VT) For B+
  Courtesy of FORD MOTOR CO.
- Is the voltage B+?
- Yes : REFER to MODULE COMMUNICATIONS NETWORK to diagnose a network concern.
- No : REPAIR circuit 296 (WH/VT) for an open. TEST the system for normal operation.