Thermostat Monitor

OBD System Description - Thermostat Monitor

System Description / Monitoring Procedure
The engine block temperature is estimated to modelize accumulated combustion heat value since engine start (based on mass intake air flow) and radiation heat value (radiation from engine, radiation when fuel shut-off, etc.). The heat exchange value between engine and engine coolant is estimated, and the engine coolant temperature is estimated. When estimated temperature reaches the specified temperature and the measured temperature is lower than criteria, the malfunction is detected.

DTC P0128: Coolant Thermostat.

DTC Detecting Condition:

DTC Detecting Condition and Trouble Area

DTC Confirmation Procedure

WARNING:
- When performing a road test, select a place where there is no traffic or possibility of a traffic accident and be very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and a tester, on a level road.

NOTE: Check to make sure that the following conditions are satisfied when using this DTC Confirmation Procedure.
- Intake air temp.: 14 °C, 6.8 °F or higher
- Altitude (barometric pressure): 2500 m, 8202 ft or less (560 mmHg, 75 kPa or more)
- Engine coolant temp. at engine start: between -10 °C and 45 °C (14 °F and 113 °F)

1. With ignition switch turned OFF, connect scan tool to DLC.
2. Turn ON ignition switch and clear DTC using scan tool.
3. Start engine and drive vehicle in 40 - 60 km/h (25 - 40 mile/h) vehicle speed and 2000 - 3000 rpm engine speed for 20 minutes or more.
4. Stop vehicle and check DTC and pending DTC.

Step 1 - 3:

Step 4 - 8:

DTC Troubleshooting

Operation:

Enable Condition:

Typical Malfunction Thresholds:

Thermostat Monitor