DTC 14

Code 14 Diagnostic Chart:

Code 14 Circuit Diagram:

CIRCUIT DESCRIPTION:

The Coolant Temperature Sensor uses a thermistor to control the signal voltage at 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 sense 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 2.5 to 3.0 volts at the ECM terminal "17." Coolant temperature is one of the inputs used by the ECM to control:

^ Open Loop timing.
^ Fuel delivery (M/C solenoid operation).
^ EFE (Early Fuel Evaporation).

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

1. Checks to see if code was set as result of hard failure or intermittent condition. Code 14 will set if signal Voltage indicates a coolant temperature above 185 degrees C (365 degrees F) for 2 minutes.

2. This test simulates conditions for a Code 15. 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 reads engine temperature in degrees Centigrade and Fahrenheit. After the engine is started, the temperature should rise steadily to about 194 degrees F (90 degrees C), then stabilize when the thermostat opens. A Code 14 will result if CKT 410 is shorted to ground. If Code 14 is intermittent, refer to DIAGNOSIS BY SYMPTOM under TESTING PROCEDURES.