You get the basic stuff like rpm, mph, and coolant temp. The more useful TPS and current IAC position is there for checking their adjustments. For tuning, you can look at O2 volts. For troubleshooting, you can look at Battery Voltage, MAF, BLM, and O2 Transitions.
You can monitor knock events but it is a little tricky. First you look at the Knock Retard which is the total degrees of retard for all knock events being processed. In other words, if a knock is detected and results in say, 1.3 degrees retard, and is followed by another knock event for 1.5 degrees then the Retard value displayed is the total for both (2.8).
When the knock sensor "senses" knocking, the computer must determine the severity so that it can apply the appropriate spark retard. The ecm uses a counter to do this. It starts counting at the beginning of the knock event and stops at the end. The displayed "ESC" value is this counter's value divided by 256. A single knock event always advances the counter but since we only see the number after it is divided by 256, the displayed ESC number might change or it might not. It depends on the knock severity.
I focus more on the retard degrees to monitor knocks. Each knock event always increases the retard. And lastly, be aware that the retard shown does not necessarily represent all knock events because of the slow ALDL data refresh rate.
