P0117

CIRCUIT DESCRIPTION
The engine coolant temperature (ECT) sensor is a thermistor that controls signal voltage to the powertrain control module (PCM). When the engine is cold, the sensor resistance is high, therefore the PCM will see high signal voltage. As the engine warms, sensor resistance becomes less and voltage drops. The voltage measured across the thermistor is interpreted as a temperature.

CONDITIONS FOR RUNNING THE DTC
^ The PCM performs this diagnostic trouble code (DTC) diagnostic continuously.
^ The ignition in the ON position.

CONDITIONS FOR SETTING THE DTC
^ The engine coolant temperature is more than or equal to 151°C (303°F).
^ All of the diagnostic set conditions are met for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
Check the harness routing for a potential short to ground. After the engine is started, the ECT temperature should rise steadily to about 85°C (185°F). Refer to Symptoms-Computers and Controls Systems. A skewed sensor could result in poor driveability complaints. Refer to Temperature vs Resistance. Symptom Related Diagnostic Procedures

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 Testing for Electrical Intermittents in Diagnostic Aids.

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

TEST DESCRIPTION

Steps 1-10:

The numbers below refer to the step numbers on the diagnostic table.
2. If the fault is still present, the engine coolant voltage will be greater than 151°C (303°F).
3. This test simulates a DTC P0117. If the PCM recognizes the high signal voltage (low temperature), the PCM and the wiring are okay.
4. This step will determine if the problem is a short to ground or a malfunctioning PCM.