DTC 14

Code 14 Chart:

Coolant Temperature Sensor Wiring Diagram:

CIRCUIT DESCRIPTION:

The Coolant Temperature Sensor (CTS) uses a thermistor to control 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 see a high signal voltage. As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature (80°C to 95°C), the voltage will measure about 1.5 to 2.0 volts at the ECM.

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

1. A Code 14 will set if the signal voltage indicates a coolant temperature less than -44°C (-47°F) for 20 seconds.

2. This test simulates a Code 15. If the ECM recognizes the low signal and sets a Code 15, the ECM and wiring are OK. If Code 14 repeats, the problem is an open circuit 410, 452, a poor connection at the ECM or sensor, or a faulty ECM.

DIAGNOSTIC AIDS:

After the engine is started, the temperature should rise steadily to about 95°C, then stabilize when the thermostat opens.
A faulty connection, or an open in circuit 410 or circuit 452 can result in a Code 14.
Codes 15 and 21 that are stored at the same time could be the result of an open circuit 452.
The "TEMPERATURE TO RESISTANCE VALUE" scale 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 drive-ability complaints. Refer to the ELECTRICAL and ELECTRONIC SPECIFICATIONS SECTION.