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

WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.

F1 CHECK CIRCUIT 1203 (BK/LB) FOR AN OPEN
- Key in OFF position.
- Disconnect: EATC Module C228a.
- Measure the resistance between the EATC module C228a-1, circuit 1203 (BK/LB) and ground.
  
  Fig 1: Measuring Resistance Between EATC Module C228A-1, Circuit 1203 (BK/LB) And Ground
  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 the EATC module C228a-26, circuit 483 (RD), C228a-14, circuit 1566 (RD/YE) and ground.
  
  Fig 2: Measuring Voltage Between EATC Module C228A-26, Circuit 483 (RD), C228A-14, Circuit 1566 (RD/YE) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to MODULE COMMUNICATIONS NETWORK to diagnose the network concern.
- No : REPAIR circuit 483 (RD) or 1566 (RD/YE) for an open. TEST the system for normal operation.