Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Pinpoint Test F: No Communication With The Electronic Automatic Temperature Control (EATC) Module
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.
- 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.
- 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.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.