P0128 OBD2 Error Code - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
What does this error code mean?
Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
Common symptoms
- Check engine light on
- Rough idle
- Change in fuel consumption
What causes it?
- MAF or MAP sensor fault
- Vacuum leak
- Oxygen sensor fault
How to fix
- Check sensor and connections
- Check vacuum lines
- Have professional diagnosis
Is it safe to drive?
Short trips at low load are acceptable. Long journeys or heavy loads are not recommended; get a diagnosis as soon as possible.
Estimated repair cost
Repair costs vary by cause and vehicle. Have a technician diagnose the issue.
Expert opinion
The code alone does not identify the faulty part; vehicle and measurement can yield different results. Have OBD-II reading and necessary checks done at a qualified workshop.
For information only. Content on this site is for general guidance; it does not replace professional diagnosis or repair. Always consult a qualified technician before making decisions about your vehicle.