Skip the auto shop - Our mechanics make house calls

Q: Check engine light with a code about insufficient temperature P0126 to the engine.

asked by on

Check engine light with insufficient coolant temp to the engine code P0126. Temp gauge reading below normal. Took it to a shop and replaced with a new thermostat as the obvious solution. Drove off and an hr later, same issue, same code. Checked and the thermostat is working fine but the check engine light is still coming on and now in cold winter temps the car is having a hard time starting, once it heats up it's ok but the check engine light stays on. Is there another sensor were missing or what could be the issue now? Thank you

My car has 154000 miles.
My car has an automatic transmission.

A: Hi there. The coolant temperature sensor (C...

Hi there. The coolant temperature sensor (CTS) is not working correctly. The sensor is sending a signal that the engine is already warm and when the engine first starts up, it needs more fuel a rich mixture to produce more heat until the engine is hot. When the engine is hot, the fuel backs off making the fuel trend more lean. I recommend replacing the coolant temperature sensor. If you need further assistance troubleshooting your cooling system, then seek out a technician, such as one from YourMechanic, that can assist you with your vehicle.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: Should I limit any journey I make in my car before getting it looked at. Could this be a serious problem?

Even though the problem was intermittent, it is very serious because if a loss of power recurs when you are on the highway or crossing a busy intersection the consequences could be disastrous. Of note, I see at least two...

Q: Car switched off but did not start when I tried to restart

Hello. First of all, rotating the engine counterclockwise could very well cause the engine to "jump time", and cause engine damage. The timing chain tensioner is not designed for this pressure, and can allow the timing chain to jump one...

Q: Do you turn the rotors when performing a brake job?

Currently, the technicians working with YourMechanic.com do not resurface brake rotors. The main reason for this is that, in order to perform a quality brake job, it is best to completely replace the rotors than it is to just resurface...

Related articles

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.
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.