P0118

Diagnostic Chart:

Schematic:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor uses a thermistor in order to control the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a voltage on the signal circuit to the sensor. When the engine is cold, the sensor resistance is high and the ECT signal voltage will be high.

As the engine warms, the sensor resistance decreases and the voltage drops. At the normal engine operating temperature, the voltage will be between 1.5and 2.0 volts at the ECT signal terminal.

The ECT sensor controls the following items:
^ The fuel delivery
^ The Torque Converter Clutch (TCC)
^ The Ignition Control (IC)
^ The EVAP canister purge valve
^ The Idle Air Control (IAC) valve
^ The electric cooling fan

CONDITIONS FOR RUNNING THE DTC
The engine run time is more than 60 seconds.

CONDITIONS FOR SETTING THE DTC
The ECT sensor indicates that the ECT is less than -40°C (-40°F) for 6.25 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.
^ A history DTC stores.
^ The coolant fan turns on.
^ The PCM will default to 20°C (68°F) for the first 60 seconds of the engine run time and then to 92°C (198°F)

CONDITIONS FOR CLEARING THE MIL/DTC
^ The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
^ A history DTC will clear after 40 consecutive warm up cycles without a fault.
^ Use a scan tool to clear the DTCs.

DIAGNOSTIC AIDS
^ The normal operating temperature for the engine cooling system is between 90°C and 95°C (194°F - 203°F).
^ Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature vs Resistance.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. This step simulates a DTC P0117. If the PCM senses the change, then the PCM and the ECT wiring are OK.
11. The replacement PCM must be reprogrammed and the Crankshaft Position System Variation Learn procedure must be preformed.