p0128
Moderate
Genesis · Sedans
Coolant Thermostat (Coolant Temperature Control) Malfunction
Quick Answer
Error code P0128 on your Genesis Sedans means: Coolant Thermostat (Coolant Temperature Control) 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 low
2
Monitor coolant temperature with scan tool
3
Perform thermostat function test
4
Inspect coolant temperature sensor operation
5
Replace thermostat if it fails to open/close properly
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 and gasket
Coolant temperature sensor
Coolant (appropriate type)
Hose clamps
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