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This is a code for the idle speed control system has anyone worked on the car recently or been around the throttle body? Check the connector to the idle speed control motor. Click the download link for more info on the code.
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You can check the solenoid valve for an open circuit. This is only for idle up. It is a duty cycle valve. If the plug is in then the valve needs to be tested. There is an active test that can be done if you have a scan tool.
If there is 12 volts at pin 2 on th ISC connector and the computer is attempting to make the ground then yes this is about it. If you look at the wiring diagram above the computer makes the ground to cycle the rotary valve. There is always the possibility of a loose pin fit at the computer or valve. Not all obd scan tools have active test capabilities. If there is a large enough vacuum leak that the ISC can not correct for then that would be the only other thing. If the valve is sticking it could set it also. Try cleaning it.
The best way to clean is to remove the throttle body and remove the valve from the bottom of it and clean with carb and choke cleaner. The hoses are water and vacuum on the valve. If you had a vacuum leak you would hear it hissing.
No the efi relay feeds many other things and the car would not run.