NHTSA Complaint #11524874 — 2019 GMC ACADIA

Thermostat gets stuck, generally in open state. AC also is disabled in this condition, soft code (no MIL) mentions "limited steering available" and temp gauge on dash goes to 0. Hard code eventually comes (solid Check Engine light on the dash). Code, MIL, and temp gauge can be cleared and fixed by disconnecting battery negative terminal and reconnecting it, and it will run consistently for a while, though it will return. Online there are no thermostat modules for this engine available (3.6L V6, also in Cadillac XT6, Buick Enclave, and Chevrolet Traverse) showing that thermostat replacement is widespread. Online forum searches also describe widespread thermostat issues for this engine, at roughly $1200 per fix. A reliable thermostat is critical for long-term engine functionality, and should not need replacement at half of design life (~75-80k miles). Though this one tends to fail open instead of close, overcooling of an engine still could have its own issues, and failing closed could lead to engine overheating.