Test D: The Electronic Automatic Temperature Control (EATC) Module Does Not Respond To The Scan Tool

PINPOINT TEST D: THE ELECTRONIC AUTOMATIC TEMPERATURE CONTROL (EATC) MODULE DOES NOT RESPOND TO THE SCAN TOOL

D1-D2:

D3-D4:

Normal Operation
The EATC module communicates with the scan tool through the medium speed controller area network (MS-CAN). Circuits 2180 (WH/BK) (MS-CAN +) and 2181 (BK/YE) (MS-CAN -) provide the network connection to the EATC module. The EATC module is only on vehicles equipped with automatic climate control. The EATC module shares the MS-CAN network with the smart junction box (SJB), the audio unit, the driver seat module (DSM), the digital versatile disc (DVD) player, the satellite radio receiver, and the instrument cluster. Voltage for the EATC module is provided by circuits 483 (RD) and 1566 (RD/YE). Circuit 1203 (BK/LB) provides ground.

Possible Causes
- Fuse
- Circuit 483 (RD) open
- Circuit 1566 (RD/YE) open
- Circuit 1203 (BK/LB) open
- Circuit 2180 (WH/BK) open (MS-CAN +)
- Circuit 2181 (BK/YE) open (MS-CAN -)
- EATC module