Upon reset, the computer has a set number of cycles it has to go through before it indicates that all sensors are checked. The cycles can vary with the number of starts, driving conditions and mils but it can be between 60-100. If pluged into before the computer has verified all the sensors, it comes back "NOT READY FOR TEST" and the emissions station will tell you to come back. Unless you have fioxed the problem, the Check Engine light eill like have come back.
2003 TJ, 33" BFG AT, 2" BL, 2" BDS spring lift, 55w DDM HIDs