Circuit Description

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

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

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

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