Hello all,
I own a 2001 Cherokee Sport.
Recently I've been having an issue with my RPM at idle. It surges anywhere from as low as 300 RPM to as high as 1400 RPM. I instantly thought this was due to a bad IAC Valve. I went and got another one, installed it, and everything seemed to be OK for the first day.
This morning, however, I noticed a check engine light, followed by a sudden rise in RPM to 1400. Great.
I checked the code and it send out P0505: Idle Air Control Motor Circuits. Awesome. I pull out the new IAC.
First of all, I checked the IAC harness connections, thinking that it could be the PCM. The harness had two pins grounded and two pins at ~12V. Seemed fine to me.
Then, I checked the resistance of both of my IAC's. The 1st and 4th pins had about 50-54 Ohms, as well as the 2nd and 3rd pins. That seems to be normal.
Lastly, I attempted to clean out the throttle body where the IAC is inserted. I cleaned it out fairly well, thinking that it could be carbon buildup that was preventing the IAC from performing properly.
Nothing.
I still get idle surges between 300-1400 RPM, as well as the P0505 code being on constantly. I've cleared it after every attempt, too.
Any suggestions on what to do next?
Thanks!

Did you get a Mopar IAC? These motors are picky about cheap ones. Also could be a vacuum leak.

Cheap ones dont typically last long or in some cases are bad right out of the box. Id suspect a non oem IAC long before i suspected the PCM. A PCM isnt something that commonly fails. That would be way down my troubleshooting list.

OEM may cost more but in my expierience in most cases you'll find they last so much longer they may actually be cheaper in the long run haha.

I actually opted for the most expensive duralast IAC valve. The leads on the IAC had the same resistance as my OEM valve.