Model: 2003 Oldsmobile Alero
The customer states the engine is overheating. Sometimes DTC P0125 Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control will be present.
Observed the engine coolant temperature gauge, and found the engine coolant temperature exceeded allowable specifications. Observed the engine, and confirmed the engine cooling fan was operating as intended during this time. Turned the engine off and inspected the cooling system but found no leaks. Removed the engine coolant thermostat, performed an inspection, and found excessive corrosion around the flange of the thermostat. Concluded that the corrosion caused the thermostat to stay closed, which caused an overheating concern.
Replaced the engine coolant thermostat and verified the vehicle operated properly. The customer’s concern did not return.
Courtesy of Mitchell 1 SureTrack Real Fixes