obd2

I found it from amazon Launch CReader 3001,here shows $24.99 Launch Launch X431 DIAGUN IV,here shows $549 That price is big difference,how to choose it ?

the obd2 port not working with chevy 06 4.2 :hissy:... the fuse (cig or ltr) working good i already tried two diff obd2 bluetooth connector but and they give me this note "Can't Connect to ECU ":weird: and already try to connect directly with protocol "SAE JI 1850 VPW" but no luck at all:nono...

can't get power to the obd2 connector. Nobody's scan tool will power up. any body know which pins the power should be on. cant find a blown fuse and everything to the best of my knowledge is working on vehicle. anybody know which fuse should power it. AA, AZ, Pep Boys, Mr Tire etc.. say its a...