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

Test Step 

1. 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.

2. 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.