DTC 14

CTS Circuit (High Temp. Indicated):

Code 14 Wiring Diagram:

CIRCUIT DESCRIPTION:

The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on a GRAY/WHITE wire to the sensor. When the engine is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see 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: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 14 will set if:

^ Signal voltage indicates a water temperature less than -48°C (-54°F) for 3 seconds.

2. This test simulates a Code 15. If the ECM recognizes the low voltage signal and sets a Code 15, the ECM and wiring are OK. If Code 14 repeats, the problem is an open GRAY/WHITE wire or light GREEN/BLACK wire, a poor connection at the ECM or sensor, or a faulty ECM.

DIAGNOSTIC AIDS:

After engine is started the temperature should rise steadily to about 95°C then stabilize when thermostat opens. A faulty connection, or an open in GRAY/WHITE wire or light GREEN/BLACK wire can result in a Code 14. Codes 14 and 22 stored at the same time could be the result of an open light GREEN/BLACK wire. The "Temperature to Resistance Value" scale on Code 15 Chart may be used to test the coolant temperature sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor. A "shifted" sensor could result in poor driveability complaints.