Circuit Description

The ECT sensor is a thermistor that monitors coolant temperature. If DTC P0116 is set, ECM will operate in a fail-safe mode, in which engine coolant is assumed to be 176°F (80°C). DTC P0116 is set when after engine has been running for 20 minutes ECM detects a temperature of less than 19.4°F (-7°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). DTC P0116 is also set when after engine has been running for 5 minutes ECM detects a temperature of less than 50°F (10°C), or detects a temperature equal to or grater than 19.4°F (-7°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). DTC P0116 is set when after engine has been running for 2 minutes ECM detects a temperature of more than or equal to 50°F (10°C) on THW circuit, and actual engine coolant temperature is 95°F (35°C). Possible causes are:

Faulty ECT sensor.
Faulty cooling system.

NOTE: If DTCs P0115 and P0116 are output together, diagnose DTC P0115 first. Inspect engine coolant temperature circuit for an open. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.