The main menu on the AP will give you the option to read the code. Do that,
and once you know what the problem is, you can clear it by choosing "re-set
When you install the unit, it automatically clears and locks out the O2 sensors
and EGR, etc, so if you have a code, you need to find out what it is.
Mine ran lean after I installed my AP, and I had to ditch my Injen CAI, which
BTW, ran ok before the AP install.
Hope this helps!