Fox T-Bird/Cougar Forums  

On Ford throttle-body Central Fuel Injection (CFI)applications, a solenoid or vacuum diaphragm isused to open the throttle linkage along with anidle-air bypass valve. Ford also uses idle-air bypass on its multipoint injection applications. Codes 12,13, 16, 17 and 19 all indicate idle speed is out ofspec (too high or too low). Codes 47 and 48indicate a fuel-mixture problem which could becaused by an air leak. The diagnostic procedure when any of these codes are found is to turn the engine off, unplug the ISC bypass air-solenoid IAC VALVE connector, then restart the engine to see if the idle RPM drops. No change would indicate a problem in the solenoid, wiring or EEC processor.  A Ford ISC solenoid can be checked by measuring its resistance. A reading of between 7.0 to 13.0ohms would be normal. Also check for shorts between both ISC solenoid terminals and the case.If the ISC checks out okay, check for battery voltage between the ISC connector terminals while the key is on. Voltage should also vary when the engine is running. No voltage indicates a wiring or EEC processor problem.