Skip the auto shop - Our mechanics make house calls

Q: Check Engine light revealed thermostat problem

asked by on

A Check Engine light system check revealed a possible thermostat problem.

A: Sounds like you have a code P0128. The co...

Sounds like you have a code P0128.

The computer monitors the warm up cycle of your engine -- it looks for your coolant temperature to rise to a certain level within a given time frame. The computer does this because it is trying to go into closed loop operation as quickly as possible leading to better fuel economy.

Now the code gets recorded because sometimes the thermostat has become stuck open or it leaks when closed. Either of these options lead to the engine not reaching the desired temperature level.

You would first test that the thermostat is indeed at fault by monitoring a warm up cycle of the engine. If it is, then I'd recommend replacing the thermostat. After replacing the thermostat, record your engines warm up cycle and compare it to before the repair to confirm your issue was resolved.

If you feel like this is a job you can handle be sure you clear the codes and reset the module after performing the repair. Please note that a lot of vehicles have special coolant fill procedures for when you refill your coolant.

If you feel uncomfortable handling this, consider having a certified mechanic, such as one from YourMechanic, come over to handle the repair for you and check if the Check Engine Light is reading any other codes.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Temperature gauges jumping and fan not running on a 2008 Avenger

Of course, the fans have to work correctly. They might not work for lots of reasons. First thing is to put in a new thermostat. Because, if you've got a stick in thermostat, the engine can get hot, but then...

Q: Check Engine codes P0310 and P0705.

The p0301 code could be caused by a bad spark plug or coil pack on the engine. I would have a technician perform a tuneup and test the coil pack to see if this clears up the misfire. As far...

Q: how many serpentine belts does a 2005 Dodge Stratus have

Hey there. Your Dodge Stratus should have two main belts. One that runs the power steering pump and one that runs everything else (i.e. crankshaft, alternator, A/C). If you need help with a serpentine belt replacement, a certified technician from...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.