Troubleshooting

DTC P0128 THERMOSTAT MALFUNCTION

CIRCUIT DESCRIPTION

DTC Detecting Condition:

If the water temperature becomes 75 °C (167 °F) or more, it is abnormal.

If not due to the thermostat malfunction, it is abnormal.

Step 1 - 2:

INSPECTION PROCEDURE

HINT: Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame 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.