On the 1995 850, as many of you know, you can read "check engine" trouble codes without a scan tool, as shown on Bay13, OzBrick, Haynes manual, etc.

In the past years I have picked up a few typical codes (PNP switch, O2 sensor, etc) and reset the system successfully as instructed. When the light came back I did the indicated repair and again reset without a problem.

A couple days ago I picked up some other codes on A1 (trans), A2 (engine) and A3 (ABS), all minor. I decided to reset because I have occasionally seen codes set during very cold weather, which never came back. But this time the procedure of resetting did not work and all the new codes remain.

I figured there is another code set somewhere that I did not read, since it's stated you need to read all codes at least once to be able to reset the system. But I can't find anything else.

I did notice that connection A6 which is supposed to be ignition, did not respond at all to checking, not even with 1-1-1.

Has anyone else had trouble resetting the system? Or reading codes via A6?
Are there functions or codes associated with A7 (besides the service interval light)?

There's no deficit in the car's operation.

Many thanks, and a great new year to all...

There is nothing in the A6 hole on that model as the Motronic engine management system does both injection and ignition. As far as not being able to reset the codes, it should be a matter of reading all of the codes until you have read the first one twice, ensuring that you read them all and then reset. Every now and then I will get a pesky one that I have to do right by the clock. By this I mean I have to stand there and watch the second hand sweep 5 seconds, release, light comes back on after 5 seconds and then hold the button down while watching the second hand sweep another 5 seconds. I know it sure sounds like over kill but I have had to do many times this way, but most of the time you can just count off "one-one thousand, two-...." and it will reset fine. Double check and make sure that you have no other codes stored. What codes is it storing by the way? As far as the functions of A7, it actually has modes 1,2,4,5,&6 and they have to do with fault codes, service light resets, data rate transfers, setting service intervals, check for odo manipulation, and a multitude of other things that are all related to the instrument cluster.