Possible causes – Drive-by-wire control system malfunction– Throttle actuator malfunction– Throttle valve malfunction– PCM malfunction Tech notes Dirty or clogged throttle body can triggered the P0638 code. Before replacing any parts try cleaning the throttle body and reset the engine

Possible causes – Failed Engine Cooling Thermostat– Engine Cooling Thermostat harness is open or shorted– Engine Cooling Thermostat circuit poor electrical connection Tech notes If there are not coolant system leaks, replaced the thermostat to fix the problem. When is

Possible causes – Failed Engine Cooling Thermostat– Engine Cooling Thermostat harness is open or shorted– Engine Cooling Thermostat circuit poor electrical connection Tech notes If there are not coolant system leaks, replaced the thermostat to fix the problem. When is

Possible causes – Failed Engine Cooling Thermostat– Engine Cooling Thermostat harness is open or shorted– Engine Cooling Thermostat circuit poor electrical connection Tech notes If there are not coolant system leaks, replaced the thermostat to fix the problem. When is

Possible causes – Faulty ambient air temperature sensor– Ambient air temperature sensor harness is open or shorted– Ambient air temperature sensor circuit poor electrical connection When is the code detected? The Engine Control Module (ECM) has detected an open or

Possible causes – Open or shorted interior temperature sensor circuit condition– Poor interior temperature sensor electrical connection– Faulty ECM /TCM Tech notes Replace DME as sensor is internal component Symptoms – Engine Light ON (or Service Engine Soon Warning Light)

Possible causes – Open or shorted interior temperature sensor circuit condition– Poor interior temperature sensor electrical connection– Faulty ECM /TCM Tech notes Replace DME as sensor is internal component Symptoms – Engine Light ON (or Service Engine Soon Warning Light)

Possible causes – Leaking fuel injector or pressure regulator– High fuel pressure condition– Faulty Oxygen (O2) Sensor– Faulty Mass Air Flow (MAF) sensor Symptoms – Engine Light ON (or Service Engine Soon Warning Light)