Trying to help a friend out today. OBD2 is not communicating with the computer I guess. I have not seen what the reader is saying but he has taken it to 3 different places and the same thing about not being able to read. The scanner powers up but shows some sort of error. Today I checked the fuse for him and also checked the chassis ground, signal ground and power supply to the obd2 plug. All is good. Have also checked for any bad wires and have not found any. Where to look next?? Thanks

 

Found the issue. Someone had messed with the OBD2 port and had the number 10 pin connector in the number 9 slot. Determined it did not have a number 9 pin through a diagram and then switched. It is now reading codes... That is the next fix.