Here is what I found on P0128 code:
- Leaking or stuck open thermostat
- Low engine coolant level
- Insufficient warm up time
- Faulty engine coolant temperature sensor
- Engine coolant temperature sensor harness is open or shorted
- Engine coolant temperature sensor circuit poor electrical connection
When is the code detected?
The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.
P0128 Hyundai Description
Coolant thermostat (coolant temperature below thermostat regulating temperature). Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.
I WOULD TAKE IT TO A DIFFERENT REPAIR SHOP, ONE THAT HAS YOUNG MECHANICS THAT UNDERSTAND TROUBLESHOOTING CODES AND SEARCHING YOUR CAR COMPUTER FOR SOFT AND HARD CODES THAT MAY BE RELATED TO THIS CODE. YOUR COMPUTER SOMETIMES KEEPS A HISTORY OF CODES.
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