Could be a stuck IAC problem. Had that with my '98 wouldn't start finally started when I held gas down and turned key. Ran rough for awhile till warmed up. Also gave me weird codes, fuel mixture, and others. IAC is on top of motor I believe 2 small bolts and a 2 wire connector. Take off and be sure it is free inside, little rod moves in and out. Spay out with WD or PB Blaster, test on battery, polarity one way it goes in reverse polarity and it goes out. Hope that works it's too easy!
