Circuit Description

WARNING: This page is about a different car, the 2003 Lexus LS 430. 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. DTC P0116 and P0125 are set when engine has been running for predetermined amount of time and sensor value is out of specified range. Possible causes are:

Faulty ECT sensor.
Engine cooling system fault.

NOTE: If DTCs P0115 and P0116 are output together, inspect ECT sensor circuits for an open. Repair as necessary. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair DTC P0115 first.