Part 2 of 2

Code Chart 14:

ECT Sensor Circuit:

CIRCUIT DESCRIPTION:
The Engine Coolant Temperature (ECT) sensor utilizes a thermistor that controls the signal voltage to the ECM. The ECM applies a voltage on circuit 410 to the sensor. When the engine is cold, the sensor (thermistor) resistance is high, therefore the ECM will sense a high signal voltage. As the engine warms, the sensor resistance becomes less and the voltage drops. At normal engine operating temperature, the voltage will measure about 1.5 to 2.0 volts at ECM terminal "B10." The Engine coolant temperature sensor is one of the inputs used to control the following:

^ Fuel Delivery.
^ Ignition Control (IC).
^ Cooling Fan.
^ Idle Air Control (IAC).
^ Torque Converter Clutch (TCC).

TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if DTC was set as a result of hard failure or intermittent condition.

2. If the ECM recognizes the open circuit (high voltage) and displays a low temperature; the ECM and wiring are OK.

DIAGNOSTIC AIDS:

^ A "Scan" tool displays engine temperature in degrees Celsius. After engine the is started, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens.
^ If the engine has been allowed to cool to ambient temperature, coolant temperature and Intake Air Temperature (IAT) may be checked with a "Scan" tool. The readings should be close to each other.
^ When DTC 14 is set, the ECM will turn "ON" the engine cooling fan.
^ If a DTC 14 is intermittent, Testing and Inspection
^ If a DTC 14 is intermittent of a hard start symptoms present, check engine coolant temperature displayed would be within 5 degrees of the ambient. If not, check the ECT sensor using the Diagnostic Aids on the next part. If sensor is OK, check connections. If connections at sensor and ECM are OK, replace ECM.