FixVault

DTC P0128 Thermostat Malfunction: Description

HINT:

This DTC relates to the thermostat.

This DTC is set when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite sufficient engine warm-up time.

DTC DETECTION CONDITION CHART

DTC No. DTC Detection Condition Trouble Area
P0128 Conditions (a), (b) and (c) met for 5 seconds (2 trip detection logic):
  1. Cold start
  2. Engine warmed up
  3. ECT less than 75°C (167°F)
  • Thermostat
  • Cooling system
  • Engine Coolant Temperature (ECT) sensor
  • ECM