Code 15 - Coolant Sensor Open
Code 15 indicates the ECM has seen the resistance of the Coolant Sensor circuit too high. This could be due to high resistance (cold engine temperature) or high voltage at ECM terminal "3" for a time longer than specified. This may cause detonation on a warm engine due to excessive spark advance, or poor driveability due to inaccurate fuel control.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- If problem still exists, "SERVICE ENGINE SOON" light will come on and Code 15 will be set.
- This test checks if fault is coolant sensor or lack of voltage to sensor. Normal reading is 5 volts across coolant sensor connector or a high temperature display (110°C) using the Scanner.
- This test determines whether low voltage at sensor connector is due to open coolant sensor circuits, or in another part of the 5-volt reference circuit. Normal voltage is about 5 volts between ECM terminals "3" to "7" or a Scanner display of high temperature (110°C).
- Normally, if voltage reading is more than 4 volts or Scanner displays high voltage (110°C), fault would be intermittent. If voltage is more than 6 volts, circuit 410 could be shorted to another voltage source.
- This test checks coolant sensor resistance. If resistance is within chart specifications, coolant sensor is okay. Check for corrosion at connector or low coolant level.