Code P0117, Coolant Temperature Sensor Temperature Low: 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 P0117 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 P0117 exist.
2. Simulates Code P0118. If control module recognizes high signal voltage, control module and wiring are okay.
3. Determines if 5-volt reference is open. This determines if there is a wiring problem or faulty control module.