Troubleshooting

CIRCUIT DESCRIPTION
A thermistor built into the engine coolant temp. sensor changes the resistance value according to the engine coolant temp.
The structure of the sensor and connection to the ECM is the same as in the intake air temp. circuit malfunction shown.
If the ECM detects the DTC P0115, it operates the fail-safe function in which the engine coolant temp. is assumed to be 80 °C (176 °C).





DETECTING CONDITIONS






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





WIRING DIAGRAM

Step 1:

Step 2:

Step 3:

Step 4:

Step 5:

INSPECTION PROCEDURE

HINT:
- If DTCs P0110 (Intake Air Temp. Circuit Malfunction), P0115 (Engine Coolant Temp. Circuit Malfunction), P0120 (Throttle/Pedal/Position Sensor/Switch "A" Circuit Malfunction) and P1410 (EGR Valve Position Sensor Circuit Malfunction) 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 warmed up or not, the air-fuel ratio lean or rich etc. at the time of the malfunction.