P0128Low urgency

Coolant Temperature Below Thermostat Regulating Temperature

Engine · Cooling System

✅ Safe to drive — schedule service at your convenience.
What this means

Your engine is taking too long to reach normal operating temperature or running cooler than expected. In the vast majority of cases this is a thermostat stuck in the open position. The fix is cheap and the part is inexpensive — but if left unaddressed it reduces fuel efficiency and can affect transmission shift points.

Likely causes
  • Thermostat stuck openMost common
  • Faulty coolant temperature sensorCommon
  • Short trips not allowing full warm-upLess common
Estimated repair cost
Thermostat + housing replacement$90 – $250
Coolant temp sensor replacement$60 – $150
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Frequently asked questions

What does P0128 mean?

Your engine is taking too long to reach normal operating temperature or running cooler than expected. In the vast majority of cases this is a thermostat stuck in the open position. The fix is cheap and the part is inexpensive — but if left unaddressed it reduces fuel efficiency and can affect transmission shift points.

Is P0128 serious?

Safe to drive — schedule service at your convenience.

How much does it cost to fix P0128?

Repair costs for P0128 range from $90 – $250 depending on the root cause and your vehicle.

Can I drive with P0128?

Yes, the vehicle is safe to drive. Schedule a repair at your convenience.