Circuit Description

WARNING: This page is about a different car, the 2002 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.

ECT sensor is a thermistor that monitors coolant temperature. If DTC P0115 is set, ECM will operate in fail-safe mode (engine coolant temperature is fixed at 176°F (80°C)). DTC is set when ECM detects an open or short in ECT circuit. Possible causes are:

Open or short in ECT sensor circuit.
Faulty ECT sensor.
Faulty ECM.

NOTE: If DTCs P0110, P0115, P0120, P0450 and P1120 are output together, inspect ECM terminal E2 (ground) circuit for an open. Repair as necessary. See WIRING DIAGRAMS article.