DTC 14

Code 14 Chart:

Coolant Temperature Sensor Circuit Wiring 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 ECM terminal "GE16" voltage will be high.

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 "GE16".

Coolant temperature is one of the inputs used to control:

^ Fuel delivery
^ Engine Spark Timing (EST)
^ Idle Air Control (IAC)
^ Torque Convertor Clutch (TCC)
^ Controlled Canister Purge (CCP)
^ Cooling Fan


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

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

1. Code 14 will set if:

^ Signal voltage indicates a coolant temperature above 140~C (285~F).
^ Engine running longer than 128 seconds

2. This test will determine if CKT 410 is shorted to ground which will cause the conditions for Code 14.


DIAGNOSTIC AIDS:

^ Check harness routing for a potential short to ground in CKT 410.


^ "Scan" tool displays engine temperature in degrees Celsius. After engine is started, the temperature should rise steadily to about 90~C, and then stabilize when thermostat opens. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.

^ Verify that engine is not overheating and has not been subjected to conditions which could create an overheating condition (i.e. overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.). The "Temperature To Resistance Value" scale in the chart may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor. A "shifted" sensor could result in poor driveability complaints.