DTC 15

Fig. 001 - Chart - Code 15 Coolant Sensor Circuit (Signal Voltage High):

Fig. 003 - Wiring Diagram for Code 15 Coolant Sensor Circuit (Signal Voltage High). VIN L:

CODE 15

COOLANT SENSOR

SIGNAL VOLTAGE HIGH

3.0L "N" SERIES

FUEL INJECTION (PORT)

The Coolant Temperature Sensor uses a thermistor to control the signal voltage to 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 the ECM will see high signal voltage.
As the engine warms, the sensor resistance become less, and the voltage drops. At normal engine operating temperature the voltage will measure about 1 to 1.5 volts at the ECM terminal C10.

Coolant temperature is one of the inputs used to control:
a. Fuel delivery.
b. Engine Spark Timing (EST)
c. Knock Control (ESC)
d. Idle (IAC)
e. Convertor Clutch (TCC)
f. Canister Purge (CCP)
g. EGR

Code 15 will set if:
a. Signal voltage indicates a coolant temperature less than -35°C (-30°F) for 4 seconds.
b. Time since engine start is more than 1 minute.

If the coolant CKT 410 opens with the ignition off, the ECM will see -35°C (-30°F) and deliver fuel for this temperature is above approx. 7°C (20°F) the engine will not start due to the rich mixture unless "Clear Flood" is used by fully depressing the accelerator.