you can buy one on ebay for around $65 or you can make one. You need a 12v LED light, three color coded banana pin wires(red,black,white or yellow), a switch that gives continuity as long as you hold down on the button and stops as soon as you release. attach or soder red wire to one of the LED leads, attach the other LED lead to one side of the switch along with white or yellow wire. The black wire goes to the other side of the switch. when testing. The black wire goes to #1 port and the red goes to #16. The white or yellow goes to which ever system port you want test. The diagnostic ports are located just behind where the right stut comes up through the fender well on the fire wall. With ignition on, hold down on the button for three seconds and wait for the flashes. One flash indicates everything is ok. To clear fault codes, go through all the fault codes and on the second time through hold down for 6 to 8 seconds for each fault code. you can find a small box to attach the light and switch to, to make it all nice and neat if so desired.