P0117

DTC P0117 Engine Coolant Temperature (ECT) Sensor Diagnostic Chart:

Engine Coolant Temperature (ECT) Sensor Wiring Schematic:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the signal voltage to the Powertrain Control Module (PCM). The PCM applies a voltage on CKT 410 to the sensor. When the engine is cold the sensor (thermistor) resistance is high, therefore, the PCM will see high signal voltage.

As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature 85°C to 95°C (185°F to 203°F) the signal will measure about 1.5 to 2.0 volts.

DIAGNOSTIC TROUBLE CODE (DTC) P0117 WILL SET WHEN
^ Engine is running over 3 seconds.
^ Signal voltage indicates engine coolant temperature less than -39°C (-38°F) for at least 0.4 second.

ACTION TAKEN (PCM WILL DEFAULT TO)
With a current DTC P0117 set, the PCM will turn the high speed cooling fans "ON" and use a default engine coolant temperature value based on run time. The default value will rise to a maximum value of 9O°C (194°F) The PCM will illuminate the Malfunction Indicator Lamp (MIL).

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Determines if conditions necessary to set DTC P0117 exist.
2. This test simulates DTC P0118. If the PCM recognizes the low signal voltage (high temperature) and the scan display reads 130°C (266°F) or more, the PCM and wiring are OK.
3. This test will determine if CKT 410 is open. There should be 5 volts present at sensor connector if measured with a digital voltmeter.

DIAGNOSTIC AIDS
A Tech 1 scan tool displays engine coolant temperature in degrees. After engine is started the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check for:
^ Poor connection or damaged harness - Inspect PCM harness connectors for backed out terminal "BF13" or "BE5", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
^ Intermittent test - With scan tool, monitor engine coolant temperature while moving related connectors and wiring harness. If the failure is induced, the display will change. This may help to isolate the location of the malfunction.
^ Shifted sensor - The "Temperature To Resistance Value" scale in the diagnostic chart may be used to test the engine coolant temperature sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor which may result in driveability complaints.
^ A faulty connection, or an open in CKT 410 or 808 will result in DTC P0117 being set.