Stuck open thermostat. Faulty engine coolant temperature sensor. Low coolant level. Faulty thermostat housing. Cooling fan running continuously.

Which cars are affected by P0128?

P0128 is most commonly reported on Vauxhall, Chevrolet, Ford, Volkswagen, Peugeot vehicles, but can appear on any make.

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P0128

Low severity

Coolant Thermostat Below Regulating Temperature

The engine is taking too long to reach normal operating temperature. This usually means the thermostat is stuck open, allowing coolant to flow continuously.

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Common causes of P0128

1Stuck open thermostat

2Faulty engine coolant temperature sensor

3Low coolant level

+2 more causes

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Commonly affected vehicles

VauxhallChevroletFordVolkswagenPeugeot

P0128 can appear on any vehicle — these are the makes where it is most frequently reported.

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Related fault codes

P0171Medium

System Too Lean (Bank 1)

P0300High

Random/Multiple Cylinder Misfire Detected

P0420Medium

Catalyst System Efficiency Below Threshold (Bank 1)

P0172Medium

System Too Rich (Bank 1)