Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

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

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


B1-B2:






B3-B5:






Normal Operation
The EATC module communicates with the scan tool through the medium speed controller area network (MS-CAN), circuits 1827 (WH/LG) and 1828 (PK/LG). The EATC shares the MS-CAN with the instrument cluster and the smart junction box (SJB). Power for the EATC is provided by redundant circuits. Circuits 298 (VT/OG) and 385 (WH/RD) provide voltage, and circuit 651 (BK/YE) provides ground.

Possible Causes
- Fuse
- Circuit 298 (VT/OG) open
- Circuit 385 (WH/RD) open
- Circuit 651 (BK/YE) open
- Circuit 1827 (WH/LG) open (MS-CAN +)
- Circuit 1828 (PK/LG) open (MS-CAN -)
- EATC module