DTC 14

Code 14 Coolant Sensor Circuit:

Fig. 028a Code 15 Coolant Sensor Circuit:

CODE 14

COOLANT SENSOR CIRCUIT

(TEMPERATURE TOO HIGH)

2.0L (VIN 1)

FUEL INJECTION (TBI)

Circuit Description: The Coolant Temperature Sensor uses a thermistor to control 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, so the ECM sees 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 the ECM terminal "E16".
Coolant temperature is one of the inputs used to control:
Fuel delivery
Electronic Spark Timing (EST)
Cooling Fan
Convertor Clutch (TCC)
Idle (IAC)

Test Description: Numbers below refer to circled numbers on Diagnostic Charts.

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 135 degrees C (275 degrees F) for 3 seconds
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. After the engine is started, the temperature should rise steadily to about 90 degrees, then stabilize, when the thermostat opens.
If the engine has been allowed to cool to an ambient temperature (overnight), Coolant and MAT temperature may be checked with a "Scan" tool and should read close to each other.
When a Code 14 is set, the ECM will turn on the Engine Cooling Fan.
A Code 14 will result if CKT 410 is shorted to ground.
If Code 14 is intermittent refer to DIAGNOSIS BY SYMPTOM