What does code P0128 mean on a Jaguar and is it safe to drive?
P0128: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature). Here's what it means on your Jaguar, 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 Jaguar
- 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 Jaguar, 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 Jaguar
Jaguar P0128 on AJ V6 and V8 engines is relatively uncommon. When it occurs it indicates a failed thermostat; genuine Jaguar thermostats are recommended as aftermarket units may not replicate the exact opening temperature spec.
Most commonly affected models
XF 2009–2015XJ 2010–2019F-Pace 2017–2021