Q: How do you reset a IAC valve in a 97 Jeep Grand Cherokee?

Make sure the engine is at operating temperature. Then you need to set the idle stop on the throttle body to the lowest setting, unless it is already there. Then to fully extend the IAC, jumper ALDL pins A and B together, and turn the key on, but do not start the car. With the key on, not running, the ECM will keep trying to fully extend the IAC. After 10 about seconds, pull the IAC connector off the IAC before doing anything else. This will capture the IAC fully extended. Now pull out the jumper in the ALDL, and start the car. Typically the minimum air idle speed is in the 400 to 500 RPM range, so you may need the manual for the spec for your model year and engine. Set the idle to spec (if you have no spec, try 450 RPM) using the throttle stop screw. Now shut the engine off and reconnect the IAC wires. The ECM does not ’know’ where the IAC present position is, so pull the ECM fuse for 20-30 seconds. The put the ECM fuse back in, turn the key on for 10 seconds and then turn the key off. This will reset the IAC valve. If you need further assistance with resetting your IAC valve, then seek out a professional, such as one from Your Mechanic, to help you.