1990 Audi 80 Quattro, OBD codes, CheckEngineLight read & reset? Fuel Injection

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1990 Audi 80 Quattro, manually read check engine codes & reset? I tried an OBDI & II code reader with an adapter to pair of 2pin connectors, but could not communicate. Found connectors under the dash by peddles, but K&L connector only has 1 wire, not 2. Looks like the problem with code reader not working. I was able to jumper the connector with wire, to read the codes off of dash, but cannot clear them with wire missing on connector? I also read some thing about putting a jumper (fuse) in the fuse socket above the fuel pump fuse. I am not sure what that is. There is a fuse like slot in the top of a module that looks like a large relay in the fuse box. I tried to jumper that with a fuse. It did not do anything with the check engine light ON when I turned the ignition on, light on. On JK Jetronic fuel injection, getting supply pressure of ~6.4bar, but Control Pressure at 0 bar. On pressure regulator, what does extra port to Control Pressure do? Maybe EHA regulator? Thank you.