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Check engine light on

'04 Buick Rainier. Friend’s diagnostic tool identifies problem as “engine coolant temperature circuit - high input”. What does this mean? Advice appreciated.

It means that the voltage the engine computer (ECM) expects to see (between 0 and 5 volts) isn’t what it should be. There may be a short in the wiring or in the engine coolant temperature sensor (ects). The repair manual will show you how to check the ects and its wiring.

I’ll check it out. Other comments/advice still appreciated in case this doesn’t lead to a solution. Thanks!