Here is a good thread, it contains the codes for pins 8 and 14 and the schematic of the code reader
http://www.peachparts.com/shopforum/showthread.php?t=107630
Its not too difficult to use, simply connect pos to pin 16 and neg to pin 1 (or battery neg) and the third wire to the desired pin. Reading the codes is the same procedure as with the built in LED/Switch.