Diagnostic Aids

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will start to open at approximately 97°C (207°F).
A resistance condition in the RCT sensor circuits may cause this DTC. This condition results in a greater voltage on the RCT sensor signal circuit, which is interpreted by the ECM as a colder RCT.