Troubleshooting

DTC P0115 ENGINE COOLANT TEMPERATURE CIRCUIT MALFUNCTION

CIRCUIT DESCRIPTION

DTC Detection Condition:

A thermistor built in the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature.

The structure of the sensor and connection to the ECM is the same as ones of the air temperature sensor.

Wiring Diagram:

Step 1 - 2:

Step 3 - 5:

INSPECTION PROCEDURE

HINT: Read freeze frame data using OBD II scan tool or LEXUS hand-held tester, 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 warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.

CHECK FOR INTERMITTENT PROBLEMS

LEXUS hand-held tester only:
By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
1. Clear the DTC.
2. Set the check mode.
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.