DTC 15

Code 15 Chart:

Code 15 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Coolant Temperature Sensor uses a thermistor to control the signal voltage to the Electronic Control Module (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 see high signal voltage. As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature (85~C to 95~C) the voltage will measure about 1.5 to 2.0 volts at the ECM.


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 15 will set if:

^ Signal voltage indicates a coolant temperature less than -44~C (-47~F) for 3 seconds.

2. This test simulates a code 14. If the ECM recognizes the low signal voltage, (high temperature) and the "Scan" reads 130~C, the ECM and wiring are OK.

3. This test will determine if CKT 410 is open. There should be 5 volts present at sensor connector if measured with a Digital Volt Meter (DVM).

DIAGNOSTIC AIDS:

A "Scan" tool reads engine temperature in degrees centigrade. After engine is started the temperature should rise steadily to about 90 degrees C then stabilize when thermostat opens. A faulty connection, or an open circuit will result in a Code 15. If Code 23 or 63 is also set, check ground CKT for faulty wiring or connections. Check terminals at sensor for good contact. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.