Working on a '96 Civic HX 1.6L. It would not pass emissions because the computer could not be scanned or connected to. All the forums I read through said that the computer in this car('96-'00 Civics and Del Sols) was not readable because it was a Japan-made one with "OBD2-a(or b?)" sytems. I spent a few hours combing over wiring harnesses trying to find one rubbed through or pulled from it's connector--no luck. Then while poking around the engine compartment fuse box I noticed a small square button looking thing in the midde. Totally unmarked, NOT on the diagram(like they intentionally didn't want you to know about it), and when I pulled on it, it came up about and 1/8 of an inch and wouldn't come out. I thought, surely this wasn't some sort of secret dealer-only trade secret for resetting a computer or disconnecting diagnostic ability? So I go and scan it--connecting...connected! No codes, everything checks out fine. So THAT was the problem--a tiny button was pushed. This kept me from being able to get my state and emissions inspections. I saw this same problem a few places while I was searching for code scanning problems, but NO ONE ever posted this fix. Good luck!

Final recap-If a scanner won't connect, check the tiny square black button in underhood fuse box by the battery--pull it up to reset/fix.

 

Post a picture of said button.

 

I'll try--it has been a while since I have loaded pics.

 

In the pic, the button is in the "UP" position. If pushed(like when you are pushing down and wiggling all the fuses and relays to make sure they all have good connection), it will keep any scanner from reading or connecting with the ECU.

 

that is not a button. that is a diode for the a/c system.

 

this ^ is correct