I have a 2000 durango with a 5.9 check light went on got code 1491(bad fan relay) took it to dearlership and told bad pcm internall fail. He wanted 1300.00 to R&R pcm I told him to go @#$# himself .Went online and got a reman.and it did myself. Took care of problem took it for a test and after about 5 miles got another code 0505 iac valve ( car runs fine) reinstalled old pcm and the only code was the 1491 nothing about 0505 my Question is why does the old pcm not pick up code 0505 and the new one does .I can reset the new one but after 5 miles or so it shows back up. Could the new pcm be bad also?

 

For how cheap the iac is, just try replacing it and see if it makes the new pcm happy. Just curious too, did you try replacing the fan relay before you jumped into replacing the pcm?

 

yes on the fan relay the only way i could get the old pcm to get the iac code was to unplug the iac then I got the code