I have read and retread the posts on zero-point-calibration and watched a couple of videos. Some say use pin position 4 on the top ow of. The connector. Others say use pin 3. All are consitant regarding pin p[osition 12 on the bottom row. Any body know which is right/ What's the risk if I do this incorrectly? Do Ijust clear the codes (disconnect negzero- battery connection) and try again?