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 Cloud Edition
For P0128, DaVinci Deluxe Cloud Edition offers the following ECU map adjustments and software solutions:
- Cold start enrichment adjust
Need to fix P0128 on your ECU?
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