Engine Control Module ECM
DTC 14 Chart:
DTC 14 Engine Coolant Temperature (ECT) Circuit:
Circuit Description:
The Engine Coolant Temperature (ECT) sensor is a thermistor which controls the signal voltage to the ECM. The ECM applies a voltage on CKT 410 to the sensor. When the engine is cold, the sensor (thermistor) resistance is high; therefore the ECM will see a 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), the voltage will measure about 1.5 to 2.0 volts.
DTC 14 Will Set When: Signal voltage indicates a coolant temperature above 135° C (270°I F) for 6 seconds.
Action Taken (ECM will default to): The Malfunction Indicator Lamp (MIL) will illuminate.
DTC 14 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 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. Checks to see if DTC was set as result of a hard failure or intermittent condition.
2. This test simulates conditions for DTC 15. If the ECM recognizes the open circuit (high voltage) and displays a low temperature, the ECM and wiring are OK.
Diagnostic Aids: Check harness routing for a potential short to ground in CKT 410.
Tech 1 scan tool displays engine coolant 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 and 452 will result in a DTC 14.
Refer to DIAGNOSIS BY SYMPTOM/ INTERMITTENTS - Intermittent Malfunctions.
The "Temperature to Resistance Value" scale in the chart may be used to test the engine 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.