Pinpoint Test F: No Communication With The Electronic Automatic Temperature Control (EATC) Module

WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.

Test Step

F1 CHECK CIRCUIT 1203 (BK/LB) FOR AN OPEN
- Key in OFF position.
- Disconnect: EATC Module C228a.
- Measure the resistance between EATC module C228a-1, circuit 1203 (BK/LB) and ground.
  
  Fig 1: Checking Circuit 1203 (BK/LB) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes: GO to F2.

No: REPAIR circuit 1203 (BK/LB). TEST the system for normal operation.
F2 CHECK CIRCUITS 483 (RD) AND 1566 (RD/YE) FOR AN OPEN
- Key in ON position.
- Measure the voltage between EATC module C228a-26, circuit 483 (RD), C228a-14, circuit 1566 (RD/YE) and ground.
  
  Fig 2: Checking Circuits 483 (RD) & 1566 (RD/YE) For An Open
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes: GO to MODULE COMMUNICATIONS NETWORK to diagnose the network concern.

No: VERIFY smart junction box (SJB) fuse 7 (7.5A) and fuse 20 (7.5A) is OK. If OK, REPAIR circuit 483 (RD) or 1566 (RD/YE) for an open. TEST the system for normal operation.