I have a 02 Chevy Avalanche, 5.3 and have had it for a month or so, the first week I had the SES light on and the readers at the parts store have shown the evap system, front wheel speed sensor and maf, (I unplugged the maf and cleaned with maf cleaner) I cleaned the speed sensor, replaced the evap valve assembly and there was no light for about a week, did some light tuning on the maf and ve tables and now I am getting the SES light back on but there is no code showing per the scanner, it will let me clear it and the light goes off but is back on in a day or so, any ideas what is going on?