Circuit Description

A thermistor is built into the Engine Coolant Temperature (ECT) sensor, of which the resistance value varies according to the ECT.

The structure of the sensor and its connection to the ECM are the same as those of the Intake Air Temperature (IAT) sensor.

HINT:

When any of DTCs P0115, P0117 and P0118 are set, the ECM enters fail-safe mode. During fail-safe mode, the ECT is estimated to be 80°C (176°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

Fig 1: DTC Trouble Detection Chart (DTC P0115/0117/0118)

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

HINT:

When any of these DTCs are set, check the ECT by selecting the following menu items on a hand-held tester: DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL/COOLANT TEMP. If using an OBD II scan tool, refer to the instruction manual.