Troubleshooting

P0128 - Thermostat Malfunction
CIRCUIT DESCRIPTION

DTC Detection Condition:

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

Steps 1 - 2:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the TOYOTA hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a 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.