QuestionIam getting code 15 on my check engine light. Can you tell
me what this is, and what sensor it is, and where is it at.
AnswerCode 15 indicates that the throttle opening motor (motor position sensor) is not operating properly. This motor is on the throttle body and controls the idle by physically opening and the throttle plate.
The reading from the motor position sensor should be about 900 mV while the car is at idle when warm. If significantly different from this, you may need to clean the throttle body and adjust the motor position sensor. I encourage you to register for an account at www.hmaservice.com and look at the procedure there, as it is not trivial, and it is extremely important that you know which screw on the throttle body has which purpose. Nonetheless, I'll go through the basic adjustment procedure here.
1. Clean the throttle body and reassemble.
2. Ensure there is slack in the throttle cable.
3. Start the engine. Turn all accessories off and wait for the engine to reach full operating temperature.
4. Observe the voltage reading from the motor position sensor. (You'll need a scan tool or voltmeter to do this).
5. Adjust the motor position sensor adjusting screw until the voltage is about 900 mV. (If the voltage never changes, you're likely either turning the wrong screw or the motor position sensor is defective).
6. Ground the timing adjustment terminal.
7. Continue adjusting the motor position adjusting screw until the specified idle speed is reached.
8. Adjust the throttle position sensor so that its reading is 500 mV.
9. Adjust the idle switch screw until the switch is open, and then back off one half turn.
10. Remove the ground from the timing adjustment terminal and check for proper idle.
