for some reason when i cycle the key to get the pcm codes it's not working. right now was the first time i knew/tried the key test haha kinda cool. it'll turn on all the guage lights and the rpm/mph needle will move. Then the odometer says ad 08 then it'll say 00 00 i tried it again and it said ad 10 then back to 00 00 then again and it said ad 13 back to 00 00. what the hell do "ad" numbers mean?? I had headers put on and my check engine light turned on. I went back to the shop and they read a code P0420 said it was the cat and turned the check engine light off. The check engine light came back on today but i was curious how to read the codes. A guy the worked at the muffler shop had a 03 diesel and showed me how to check codes on his. it said some code and then - - - - - - he tried it on mine and nothing happened. I did a search and found some things about the P0420 code but nothing helpful. I have to take it back to the muffler shop sometime this week. They want to check the 02 sensor wires, they had to splice/soder to add extensions due to the long tubes. When he hooked up the diagnostics tool it gave a reading on all 4 cats and they were all functioning so who knows. I'm still running the cats and they had to move them a foot or so back so i'm thinking that might be why (even though there still getting hot)

i found this link that gave information!?! https://dodgeforum.com/m_289309/mpag.../tm.htm#290431