Troubleshooting

DTC P0128 COOLANT THERMOSTAT (COOLANT TEMP. BELOW THERMOSTAT REGULATING TEMP)

CIRCUIT DESCRIPTION

DTC Detection Condition:

If the water temperature doesn't reach 75 °C (167 °F) even after warming up, it is abnormal. If not, due the thermostat malfunction, it is abnormal.

Step 1 - 2:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.