Am having the same problem with mine
It the same MY as yours

I checked the lines, clean the tb, and nothing
I think i got a defective iac, so are the rockauto iac good?
The iac i got came from a red and white box idr the brand.

 

Honestly I have bought so many I dont remember. I think its the wiring harness
just cant believe every single one is bad or wont work.
Sorry I cant be of more help yet, but when I figure it out I will be posting

 

I was looking at rockauto they had some connectors for the IAC for 8-15 bucks

 

We have been working on our P0505 code for a few years now. We have tried so many things. Ours is a 2000 Dodge Durango 5.9. Just wanted to chime in and let you know you aren't the only one. We have replaced the iac 2 times.

 

I cleaned the TB. installed the Standard IAC. I run the truck without the Air filter, I can hear the solenoid kick in at idle and out upon acceleration.

I did a 15 min battery disconnect for PCM clearing. its ok but after I turn it off. it come back on. I run the DTC, and P0505, try to clear the code, I can't.

am going to check the cable, possible change it. I hope this doesn't end up needed to reflash the PCM.