Hello , I picked up a nice 96 2500 conversion van that had a fast and roaming idle . Other than that issue the van runs excellent and one way or the other is going to be my fishing and camping truck.
The issue I am having is , the engine light was on so I used a generic obd scanner to see the code was 505 , additional info was any one of the coils in the iac is shorted to either positive or ground.
New iac from the former owner in the glove box the van idled exactly the same , known good iac of my dakota , same idle . Tested and even tried the dakotas tps on the van , exact same idle . What I found is the iac connector 3 wires are 12v and one ground. What I thought they should be is 2 hot and 2 grounds going to the iac .
I ordered a new pigtail just because I couldn't find one in stock local but my question is how common is it for the computer to short internally ?
Thanks , new to the site but with this vam I'm sure to not be a stranger

 

Yep, PCM controls IAC by switching current on/off on those two circuits. (four wires) If you have power on three of 'em, with the IAC unplugged, then you have a short somewhere. Unplug the other end of the connector from the PCM as well, and test the wires to see if any of them are shorted together. Might be an easy fix. If the wiring is good though, yep, failed PCM.

Welcome to DF!

 

Also just discovered there is no charcoal canister at all on the van , the bracket is there and one line coming from the egr , and a vacum line that comes from where the can would be, it runs through holes on the crossover and just ends in mid air before the rear end. Don't think it's my iac problem but I mean there should be one there right ?

 

Yep. Should be one there. Not sure how concerned the 96 PCM will be about it's absence though. It doesn't have a leak detection pump, so, it simply may not care.

 

Thanks, that's along the lines I was thinking , no evap code at all , just the constant 505 iac . The line was sucking vacum though and plugging it did drop the idle a little and the iac seemed to be able to keep its range tighter but still throws the code fast. I checked continuity between each wire by back probing the pcm connectors that match. All wires had continuity to each end but not with any other wire . Running it switches between 12v on 3 wires and at tines all 4 .
in the foolish part of my mind I want to start with tps and the pick up but the older part of me is saying just order the pcm. I already ordered a pigtail because the price was right . For curiosity I will change it before the pcm would get here anyways . I guess in the down time I will start with new vac lines and a tune up . This van is exactly what I want and need , price was right also so dependability is going to be first. Makes it easier to put money Into because I have a 96 dakota that never let me down so I'm not in a hurry . Thanks for replying and I'll upload a few pics if I can

 

Well, if the wires test good, that leaves...... the PCM. I think you need to bite the bullet, and get one comin'.

 

I just went through this. The service manual said the same thing.
The PCM fixed it.

 

New pcm came in from Protech and solved my issue in minutes! Passed emissions and inspection today. Guys were good and were in the 5 to 8 days time they quoted even though they called and informed me the core they were going to rebuild and program for me was un usable . Rather they caught it rather than me having to discover it had issues . After the Vin number the only other question they needed was overdrive or no . Class act!
Thanks for the input and time to work on the little things, some mods or whatnot. Legal and no engine light!

 

Awesome.