Possible causes

– Leaking or stuck open thermostat
– Low engine coolant level
– Insufficient warm up time
– Faulty engine coolant temperature sensor
– Engine coolant temperature sensor harness is open or shorted
– Engine coolant temperature sensor circuit poor electrical connection

Tech notes

If cooling system is not leaking and the fluid level is OK, replacing the thermostat usually takes care of the problem.

When is the code detected?

The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0128 Description

Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.

P0128 Information for specific makes

P0128 ACURA
P0128 HONDA
P0128 BMW
P0128 CHRYSLER
P0128 JEEP
P0128 DODGE
P0128 SATURN
P0128 FORD
P0128 HYUNDAI
P0128 INFINITI
P0128 NISSAN
P0128 ISUZU
P0128 KIA
P0128 LEXUS
P0128 TOYOTA
P0128 SCION
P0128 MAZDA
P0128 PONTIAC
P0128 MITSUBISHI
P0128 SUBARU
P0128 VOLKSWAGEN
P0128 AUDI
P0128 JAGUAR
P0128 BUICK
P0128 CADILLAC
P0128 CHEVROLET
P0128 GMC
P0128 SATURN