p0128
Moderate
Mitsubishi · Sedans & Cars
Coolant Thermostat (Coolant Temp Regulating System) Malfunction
Quick Answer
Error code P0128 on your Mitsubishi Sedans & Cars means: Coolant Thermostat (Coolant Temp Regulating System) Malfunction. This is usually fixable — see the step-by-step guide below.
Affected Models
Likely Causes
How to Fix It
1
Check coolant level and top off if needed
2
Monitor coolant temperature with scanner
3
Inspect radiator hoses for leaks
4
Test thermostat operation by warming engine
5
Check water pump operation
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
Temperature sensor
Radiator hoses
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