DTC 15

Code 15 Chart:

Wiring Diagram For CTS:

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 high signal voltage. As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature 85 to 95°C (185 to 203°F) the voltage will measure about 1.5 to 2.0 volts.


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

1. A Code 15 will set if:
^ If engine runs longer than 30 seconds.
^ Engine coolant temperature is below -33°C (-27°F) for three seconds.

2. This test stimulates conditions for a Code 14. If the ECM recognizes the grounded circuit (low voltage) and displays a high temperature, and the "Scan" tool reads 130°C (266°F) or above, the ECM and wiring are OK.

3. This test will determine if circuit 410 is open. There should be five volts present, measured with a DVM, at the sensor connector.


DIAGNOSTIC AIDS:

^ If a Code 21 or 23 is also set, check circuit 452 for faulty wiring or connections. Check terminals at sensor for good contact.
^ A "Scan" tool displays engine temp. in degrees centigrade. After engine the is started, the temperature should rise steadily to about 90°C then stabilize when thermostat opens.
^ The "Temperature to Resistance Value" scale above can be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor could result in driveability complaints.
^ If a Code 15 is intermittent, - Intermittent Malfunctions