p0128
Moderate
Kia · Sedans
Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temp)
Quick Answer
Error code P0128 on your Kia Sedans means: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temp). This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Check coolant level and top off if low
2
Monitor coolant temperature with scanner during startup
3
Feel upper radiator hose for heat circulation
4
Replace thermostat if stuck open
5
Test coolant temperature sensor readings
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Thermostat
Coolant
Coolant temperature sensor
Gasket
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