Troubleshooting

CIRCUIT DESCRIPTION

Detection Item:

A thermistor built into 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 in the intake air temperature circuit malfunction.
If the ECM detects the DTC P0115, it operates the fail-safe function in which the engine coolant temperature is assumed to be 80 °C (176 °C).






HINT: After confirming DTC P0115, use the OBD II scan tool or LEXUS hand-held tester to confirm the engine coolant temperature from CURRENT DATA.

Wiring Diagram:

Steps 1 - 2:

Steps 3 - 4:

Step 5:

INSPECTION PROCEDURE

HINT:
- If DTCs P0110, P0115, P0120 and P1410 are output simultaneously, E2 (sensor ground) may be open.
- Read freeze frame data using LEXUS 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.


CHECK FOR INTERMITTENT PROBLEMS

LEXUS hand-held tester only:
By putting the vehicle's ECM in the check mode, 1 trip detection logic is possible instead of 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.