P1114

DTC P1114 ECT Sensor CKT Intermittent Low Voltage




Circuit Description
The Engine Coolant Temperature (ECT) sensor contains a device which changes its resistance based on temperature. This device is called a thermistor. The ECT sensor is mounted in an engine coolant passage. The ECT sensor has a signal circuit and a ground circuit. The VCM applies a voltage (approximately 5 volts) on the signal circuit to the sensor. The VCM monitors the changes in this voltage caused by changes in the resistance of the sensor. This allows the VCM to determine coolant temperature.

When the coolant is cold, the sensor resistance is high. The VCM will detect a high signal voltage due to this high resistance. This signal voltage is converted by the VCM into temperature. A high signal voltage will be seen on a scan tool as a low temperature.

When the coolant is warm, the sensor resistance is low The VCM will sense a low signal voltage which is converted by the VCM into a higher temperature. At normal operating temperature, the VCM should measure about 1.5 - 2 volts on the ECT signal circuit.

This DTC is designed to detect intermittent low voltage signals on the ECT sensor signal circuit.

Conditions for Running the DTC
Engine run time is greater than 5 seconds.

Conditions for Setting the DTC
The VCM detects an intermittent low ECT voltage while the engine is running and run time exceeds 5 seconds.

Action Taken When the DTC Sets
The VCM stores the DTC in History if the VCM detects an intermittent problem.

Conditions for Clearing the MIL/DTC
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature exceeds 70 °C (160 °F) during the same ignition cycle.
- Use the scan tool Clear Information function.

Diagnostic Aids
An intermittent short to ground in the ECT sensor signal circuit could result in a DTC P1114.

The scan tool displays the engine temperature in degrees centigrade. After the engine is started, the temperature should rise steadily to about 90 °C (194 °F) then stabilize when the thermostat opens.

Use the Temperature vs. Resistance Value scale in order to test the coolant sensor at various temperature levels in order to evaluate the possibility of a skewed or mis-scaled sensor. A skewed sensor could result in poor driveability complaints. Refer to Temperature vs Resistance.

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 5:

Steps 6 - 9:

Test Description
The numbers below refer to the step numbers on the diagnostic table.

2. If the ECT sensor voltage is less than 0.24 volts, then the conditions for the DTC are still present.
3. If any other non-intermittent DTCs are set go there first.