P0118

Circuit Description
The Engine Coolant Temperature (ECT) sensor contains a semiconductor device which changes resistance based on temperature (a thermistor). The ECT sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors changes in this voltage caused by changes in the resistance Of the sensor to determine engine coolant temperature.
When the engine coolant is cold, the sensor (thermistor) resistance is high, and the PCMs signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the PCM will sense a high signal voltage (low temperature). When the engine coolant is warm, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the PCM to sense a low signal voltage (high temperature).

Conditions for Running the DTC
Engine run time longer than 3 seconds

Conditions for Setting the DTC
^ The ECT sensor signal indicates an engine coolant temperature less than -13°C (9°F).
^ Above condition present for at least 10 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL Off after three consecutive drive trips that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any Other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids
Check for a skewed or mis-scaled ECT Sensor.
If DTC P0118 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set.


Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
2. Verifies that the malfunction is present.
3. If DTC P0118 can be repeated only by duplicating the Failure Records conditions.
12. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.