Troubleshooting

P0128 - Thermostat Malfunction

CIRCUIT DESCRIPTION

DTC Detecting Condition:

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

Step 1 - 2:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the TOYOTA hand-held tester or OBDII 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.