Check engine light is on with code P0128, coolant thermostat?

Tiny
ELIZABETHBROWN87
  • MEMBER
  • 2015 HYUNDAI SONATA
  • 2.4L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 40,000 MILES
Hi, my check engine light is on and I’m getting a P0128 error code. Coolant level is fine. My temperature gauge is reading normally. Starting cold and then heating up in 5-7 minutes of driving to sit in the middle of the gauge. No rapid fluctuations or signs of overheating. A/C and Heat are working normally. Does my thermostat need to be replaced or could it be something else? Thank you!
Monday, September 26th, 2022 AT 11:53 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
Since the engine is heating up quickly, I would say the engine coolant temperature sensor needs to be replaced. Start by draining the coolant, here is a guide to help you through the steps and the instructions and location of the sensor and the images below.

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the images (below). Please let us know what happens. Clear the codes once the job is complete.

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Monday, September 26th, 2022 AT 4:22 PM

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