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.

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!
  • Home
  • Questions
  • Check engine light with a code about insufficient temperature P0126 to the engine.

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: Engine light came on

The "Check Engine Light" indicates a fault being stored in the engine computer. A triangle shaped light with a circle around it indicates a fault in the electronic stability control. To diagnose these issues the faults will need to be...

Q: Belt, pump, and gauge problems

Hello! There is likely an issue wth the oil pressure sensor causing the flashing Oil Light. I suggest having a technician test the sensor by the use of a multimeter. Also, be sure to have the oil level checked; a...

Q: My trunk light does not come on

The tests you have done so far pretty much tell the tale. If you are not receiving full voltage at the trunk light, then that voltage is being cut off somewhere. Where did you test the voltage from? If it...

Related articles

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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...