Code P0118, Coolant Temperature Sensor Temperature High: Notes

Coolant sensor uses a thermistor to control signal voltage to control module. Control module applies and monitors a 5 volts to sensor. When engine coolant is cold, sensor (thermistor) resistance is high and control module will sense a high signal voltage. As engine coolant warms, sensor resistance becomes less and control module voltage drops. With Code P0118 set, control module will turn cooling fans on and use a default engine coolant temperature value based on run time. Control module will illuminate Malfunction Indicator Light (MIL).

1. This step determines if conditions necessary to set code exist.
2. Simulates Code P0117. If control module recognizes low voltage, control module and wiring are okay.