2010 Subaru P0128: What It Means & Is It Safe to Drive?
P0128 on the 2010 Subaru: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature). Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
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What this code means
The engine is not reaching normal operating temperature in the expected time. Usually a stuck-open thermostat.
Common causes on the 2010 Subaru
- Thermostat stuck open
- Coolant temperature sensor fault
- Low coolant level
Symptoms
- Check Engine Light
- Heater may blow cold
- Poor fuel economy
- Temperature gauge stays low
Typical fixes
- Replace thermostat
- Replace coolant temperature sensor if faulty
- Refill coolant and check for leaks
Repair cost range
For a 2010 Subaru, repairs for P0128 typically fall between $100 and $350, depending on the root cause and labor rates in your area.
Known issues on Subaru
Subaru P0128 on EJ engines can result from a thermostat that sticks open or a coolant temperature sensor fault. Subaru recommends OEM thermostats due to the boxer engine's cooling system sensitivity; replace the thermostat first as it's low cost.
Most commonly affected models
Outback 2010–2016Forester 2009–2016Impreza 2008–2016