Circuit Description
The engine coolant temperature (ECT) sensor is a thermistor that is located in the lower coolant passage of the engine cylinder head. The ECM continuously monitors the voltage drop across the resistor as it varies with the resistance of the sensor. This sensor is used for fuel/ignition control, hot/low coolant light, coolant gage, and fan. The ECM sets this DTC when the signal being received is higher than expected.
DTC Parameters
DTC P0118 will set when:
| • | ECT less than -39°C (-38°F) |
| • | Engine running longer than 4 minutes |
P0118 is a (type B) DTC.
Caution: To avoid the danger of being burned, do not remove the cap while the engine, radiator, and surge tank are still hot. Scalding fluid and steam can be blown out under pressure.
Important: The ECT signal is continuously checked when ignition is On.
Diagnostic Aids
To loacte intermittent failure use scan tool to monitor the ECT temperature with ignition On, engine Off.
Wiggling wires while monitoring ECT temperature may locate area where an open or short to voltage exists.
Start engine and observe ECT reading on scan tool. Under normal conditions, it should rise smoothly to 88°C (190°F).
ECT may be compared to IAT with scan tool if engine has cooled overnight. They should be within 6°C or 10°F of each other with the ignition On and engine Off.
