Idle Speed Control (ISC) Motor

A malfunction in the ISC circuit will set a diagnostic trouble code. For testing procedures, see TESTS W/CODES - 4.0L article in this section. To check ISC for proper operation and ISC plunger adjustment, perform the following:

1. Install Tech 1 scan tester. Turn ignition on, with engine off. Check for stored Diagnostic Trouble Code(s) (DTCs). If any code(s) is present, diagnose trouble code first. If code(s) is not present, go to next step.
2. Using scan tester, select "Misc Test, ISC System F3". Select function "F3" to retract ISC plunger and "F2" to extend ISC plunger. If plunger did not retract or extend, refer to DTC 30 in the TESTS W/CODES - 4.0L article in this section. If ISC plunger retracted and extended as commanded, go to next step.
3. Start engine. Using scan tester, select function "F3" to retract ISC plunger. If engine speed drops to less than 700 RPM or engine stalls, go to next step. If engine speed increases to greater than 700 RPM, check for intake manifold vacuum leak. If no leaks are present, replace throttle body.
4. Turn engine off. Turn ignition on, with engine off. Select "Misc Test, ISC System F3". Select function "F3" to retract ISC plunger. Wait 10 seconds, then record Throttle Position (TP) sensor minimum idle value. Select function "F2" to extend ISC plunger. Wait 10 seconds, then record TP sensor maximum extend value. Subtract TP sensor minimum value from TP sensor maximum value and record ISC authority.
5. IF ISC authority is 10-11 degrees, ISC is okay. If ISC authority is less than 10 degrees, adjust ISC plunger out (counterclockwise) and recheck ISC authority (10-11 degrees). Perform idle learn procedure.
6. If ISC authority is greater than 11 degrees, adjust ISC plunger in (clockwise) and recheck ISC authority (10-11 degrees). Perform idle learn adjustment.