What does code P0128 mean on a Infiniti and is it safe to drive?
P0128: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature). Here's what it means on your Infiniti, what usually causes it, what repairs typically cost, and how safe it is 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 for your Infiniti
- 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 Infiniti, repairs for P0128 often fall between $100 and $350, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Infiniti
Infiniti P0128 on VQ35/VQ37 engines points to a failed thermostat in most cases. Nissan/Infiniti thermostats are generally reliable; confirm the coolant temperature stays low with a scan tool before replacing.
Most commonly affected models
G35 2003–2007G37 2008–2013QX60 2013–2018