Q: P0128 code, but coolant is full

asked by on

I got this code when I checked the computer on my vehicle: "P0128". I looked up the code and it means "Coolant Temperature Below Thermostat Regulating Temperature". This code showed up about a week ago. I cleared it, and the vehicle actually passed inspection right after.

Later the same day, the Check Engine Light came on again, with the same P0128 code. My coolant level is just fine, so I apparently don't have any leaks. What might be causing the code? Thermostat perhaps?

This is most likely caused by the thermostat partly stuck open. The coolant sensor would need to be tested to make sure it is not bad, though. I would test the thermostat at the housing with a temperature tester, and compare it to the coolant sensor readings.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. P0128 code, but coolant is full

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Check Engine code for catalytic converter.

This can be because the catalytic converter is bad or the sensor is defective. A qualified mechanic would have to scan the vehicle and check for broken up or rattling converter signifying its coming apart inside.

Q: Coolant leak causing overheating

If you can see the leak, that is where you need to start. A cooling system cannot operate efficiently with a leak or low level condition. If there are no leaks, the problem could be the thermostat, this is the...

Q: Are the variable valve timing solenoid and the camshaft sensor the same?

Hello. The variable valve timing and the camshaft position sensor are two separate sensors. The camshaft position sensor is more towards the front of the engine and is a lot easier to replace. The variable valve timing sensor is a...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.