Mixed signals from a vehicle can be frustrating, such as having a message on the dash saying the engine is hot when it’s not. SureTrack community member sportsman850sp had a Buick Lucerne in their shop that would display “Engine Hot A/C Off” on the dash as soon as the vehicle was started cold. They posed the question to the community, and with the help of fellow community member dmckemie12, Richard_C and others, they were able to resolve the issue quickly.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
2009 Buick Lucerne CXL 3.9L
Title
Engine Hot message on dash, replaced thermostat.
Complaint
Customer states that vehicle displays “Engine Hot A/C Off” message on instrument panel.
Diagnostic Steps Performed/Parts Replaced
Started engine cold and Engine Hot A/C Off message appears on instrument panel. Cooling fans running all the time. Looked at engine data and temperature reads 140 degrees F. Engine is not running hot.
Best Answer from Community Member dmckemie12
Check the ECM for DTCs, it most likely has a P0128 stored and needs a t-stat. If the P0128 was logged the previous drive cycle, upon the next ignition it gives a message of “Engine Hot A/C Off’ and disables the gauge and compressor. Even though the DTC is for the engine running too cool, and it knows it, it does that.
Cause
Bad thermostat causing car to run too cool even though giving message that engine was hot.
Correction
Replaced thermostat and cleared codes, message no longer displays.
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