Does a 1993 90 with an MMS200 ECU have the check engine light connected to the L-line? (My check engine light flashes as VAG-COM is trying to connect.) If so, what do I need to do to get it to work properly? If not, what could be my problem? Single reading works, but not measuring blocks.

I also cannot connect to the ABS nor airbag controllers at all. Climate control seems to work fine, but haven't tried anything but pulling codes there.

Yes, registered version.<ul><li><a href="http://forums.audiworld.com/vag/msgs/4179.phtml">Original thread describing symptoms.</a></li></ul>

Airbags and Engine should talk, however, these old cars can be quite fussy about the interface.

Bentley says ABS on the 90 is diagnostics-capable as of model-year 1994, so I think you're out of luck on that one.

-Uwe-

Most of the pertinent information is on the link, including interface type.

Thanks. :)

L-line is connected to check engine light -- that's only an issue for some dual-K interfaces.

Since we have others with Audi 90's using ISO-COMs, it sounds like there is some issue with your particular car. I'd check continuity of wiring between diagnostic plugs and ECU harness for K and L.

-Uwe-

Have you tried Measuring Block 000? On some early ECU's 000 and single readings were all there was. Since you can get to the start screen, post the ECU part #, and I will see if I have any info.

Re no airbag coms: In early 90's Audi the airbag controller was not tied into the diagnostic ports used to access engine and HVAC. Instead there were seperate white and black connectors buried in the center console foward of the shifter. They can be very hard to find! If your car was involved in the "KF" airbag controller recall this will be the case.

Measuring block 000 does not work. According to my Bentley measuring blocks should work, as a necessary adjustment (CO potentiometer) is made via measuring block 008. I've been able to fake it by using single readings 00 and 01, but measuring block 008 is the proper way to do it.

Yes it should have measuring blocks available. It appears this controler was a modification of 4A0 906 266 used on the 100 in MY 92, but it was again modified to 8A0 906 266 B within MY 93 on the 80-90. This was a substantial modification which removed the CO2 adjustment and added OXS learning and soft codeing.
Interesting that it won't show you measuring blocks, but does't drop the session. Like Uwe said you will have to trouble shoot the K line. Try first unpluging the HVAC. Also make sure the power (red and brown) in the black connector is good with ISO-COM plugged in.