P0128
Coolant Thermostat (Coolant Below Regulating Temperature)
System: Cooling
Severity: medium
What does P0128 mean?
The DTC P0128 (Coolant Thermostat (Coolant Below Regulating Temperature)) is a fault code stored by the ECU when it detects a thermostat stuck open condition in the cooling subsystem. It is commonly seen on European and Asian vehicles using Bosch, Continental, Siemens or Denso ECUs.
Common causes of P0128
- Stuck-open thermostat
- Failed coolant temp sensor
How to fix P0128
Replace thermostat.
Tuning approach with DaVinci Deluxe
For P0128, DaVinci Deluxe offers the following ECU map adjustments and software solutions:
- Cold start enrichment adjust
Need to fix P0128 on your ECU?
DaVinci Deluxe is professional ECU tuning software trusted by 800+ workshops. Lifetime license €299, 10 minutes free trial.
See pricing Try free