Powertrain Controls - ECM/PCM

Code Chart 14 Engine Coolant Temperature Sensor Circuit:

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Code Chart 14:

CHART 2 OF 2

Engine Coolant Temperature Sensor Wiring Circuit:

Circuit Description:
The Engine Coolant Temperature (ECT) sensor utilizes a thermistor to control the signal voltage to the Engine Control Module (.ECM). The ECM applies a reference voltage on CKT 410 to the sensor. When the engine is cold, the sensor (thermistor) resistance is high. The ECM will then sense a high signal voltage.

As the engine warms up, the sensor resistance decreases and the voltage drops. At normal engine operating temperature, the voltage will measure about 1.5 to 2.0 volts at ECM terminal "B10".

Engine coolant temperature is one of the inputs used to control the following:
^ Cooling fan.
^ Idle Air Control (IAC).
^ Fuel delivery.
^ Torque Converter Clutch (TCC).
^ Ignition Control (IC).

A separate thermistor within the ECT sensor provides a signal to the engine coolant temperature gage located in the instrument panel.

DTC 14 Will Set When:
^ The engine has been running for at least 2 minutes.
^ Signal voltage indicates an engine coolant temperature below -30°C (-22°F) or above 144°C (291°F).

Action Taken (ECM will default to): Malfunction Indicator Lamp (MIL) illuminates. ECM will default to 65°C, engine coolant temperature (Tech 1 scan tool will not show defaulted value). ECM will turn "ON" the engine cooling fan.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step checks to see if DTC 14 is the result of hard failure or intermittent condition.
2. If the ECM recognizes the grounded circuit (low voltage) and displays a high temperature: the ECM and wiring are OK.
3. This test will determine if there is a wiring problem or a faulty ECM. If CKT 452 is open, there may also be another DTC(s) stored.
4. This step checks to see if DTC 14 is the result of hard failure or intermittent condition.
5. If the ECM recognizes the open circuit (hjah voltage) and displays a low temperature the ECM and wiring are OK.

Diagnostic Aids: A scan tool should display engine temperature in degrees Celsius.

After the engine is started. the temperature should rise steadily to about 90°C (194°F), then stabilize when the thermostat opens.

If DTC 14 is intermittent, refer to "Diagnosis By Symptoms." Testing and Inspection

^ If DTC 14 is intermittent or a "Hard Start" symptom is present, check engine coolant temperature with a scan tool on a cool engine. Temperature displayed would be within 5 degrees of the ambient. If sensor is OK, check connections. If connections at sensor and ECM are OK, replace ECM.