P0117

DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit High (Low Temperature Indicated):

Engine Coolant Temperature (ECT) Sensor Circuit High:

Circuit Description
The Engine Coolant Temperature (ECT) sensor is a thermistor which controls the signal voltage to the VCM. The VCM applies a voltage on CKT 410 to the sensor. When the engine is cold, the sensor (thermistor) resistance is high; therefore, the VCM will sense a high signal voltage and coolant temperature will be indicated.

As the engine warms, the sensor resistance becomes less and the voltage drops indicating high coolant temperature. At normal engine operating temperature (85°C to 95°C), the voltage will measure about 1 to 2.0 volts.

DTC P0117 Will Set When
Signal voltage indicates an engine coolant temperature less than 3&C (-36°F) and engine run time is greater than 3 seconds.

Action Taken (VCM will default to)
Coolant temperature will default to 0°C (32°F) for the first 90 seconds on a cold engine and then to 65°C (149°F) after 90 seconds has elapsed.

DTC P0117 Will Clear When
Conditions for fault are no longer present and Tech 1 clear DTCs function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and Fuse #9 (ECM B) fuse is removed for 10 seconds.

DTC Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the fault is still present, engine coolant temperature will be less than -38°C (-36°F).

2. This test simulates a DTC P0118. If the VCM recognizes the low signal voltage (high temperature), and the Tech 1 scan reads 135°C (275°F) or above, the VCM 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 J39200. This will determine if there is a wiring problem or a faulty VCM.

Diagnostic Aids
A Tech 1 scan tool displays engine temperature in degrees centigrade. After engine is started, the temperature should rise steadily to about 90°C then stabilize when thermostat opens.

A faulty connection or an open in CKTs 410 or 452 will result in a DTC P0117. Refer to "Intermittents". - Intermittent Malfunctions

The "Temperature To Resistance Value" scale at the right may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor could result in poor driveability complaints.