Howdy,

Got a 2001, 5.2 that is getting this code. My truck is idling high, but only about 100-200 rpm higher than it should be (750-850 rpm). I've replaced the iac, cleaned the ports and reset the pcm. If it is a vacuum leak, im guessing its really small, as I didnt detect any with carb cleaner. When I searched the forums the rpms in those cases are significantly higher. Just curious where I should look next. Thank you kindly in advance.

 

P0505 Idle Air Control Motor Circuits
If you are still getting the code after clearing the code there is probably an issue with the plug or wiring to the iac.

 

I have also seen PCMs fail on one or both of the IAC control circuits......

 

Thank y'all for the responses, I did a couple more diagnostic checks and I think I have at least a plan of attack.

First thing I did was put the truck in the On position and check for voltage from 2 of the 4 IAC ports. Which I had.

I then started the truck with the IAC unplugged, and it basically ran exactly the same as when it was plugged in.

I went and also checked voltage on the IAC ports and I was getting voltage from all 4 ports. It wouldn't stay on constantly, but I believe that is to be expected. This makes me think the PCM is working.

So I think my next step would be to replace the IAC (it's only a year old, but was one of those cheap Advance Auto Parts Driveworks IACs) and if that fails, then it'll probably need a new PCM. Does this seem like a logical approach?

Thank you all for the feedback!

 

Sounds like a good plan. Get a genuine Mopar IAC. I have had no success with the aftermarket fellers.

 

Thanks for the info.. I did replace the IAC this morning, and after resetting the PCM, the truck started fine, when it warmed up it was at 650 RPM. Shut the truck off, went to turn it back on, dies immediately. Seems like it might be a defective IAC, as this was the symptom when the original IAC failed. Does that seem like a reasonable conclusion? Was a Mopar part, but got it off eBay, so might be a cheap knockoff.

 

Usually it will say 'mopar' or something similar, on it somewhere, if its genuine... But, even that is no guarantee. I like to reset the pcm, start the truck, let it figger out idle, and then run for a bit.......

 

So, just an update. (Sorry for the slowness of it.)

The DTC is still there. I cleared it, drove it 3000 miles from Texas to Wisconsin and had no problems. I went and checked continuity and that was solid, with fairly low resistance. When I unplug the IAC and clear the DTC, the P0505 comes back right away. I'm fairly certain at this point that the PCM is the issue. I was just wondering if there was any last checks I should do to see if it could be something other than the PCM?

 

IAC is a four wire connector. PCM controls it by switching power/ground on those four wires to move the pintle. So, ignition on, you should see power on two of those wires, and ground on the other two. If you don't, and know the wiring is good, bad PCM.

 

I just checked, and I do have 12v to 2 wires, and 0.02 to the other 2. I'm assuming that's fine, unless you think that 0.02 might be a sign of a grounding issue?