Engine Control Lamp (Check Engine) does not glow!

Yesterday I was with our problem child with smog test and the exhaust gas values are so wonderful (clear, after new candles, cables, lambda probe, oil change, filter change, etc., there was nothing to be ...) only the Mr. Prüfer could not finish the test positively, because the engine control ("check engine") does not light up - so never, even if it should actually (at ignition, I suppose).

The question now is: what could it be?

Is it "simple" a broken pear, or is there still a fuse that may have given up the mind?

I've been searching through the search, but I couldn't find a thread with a suitable theme. Lt. Documents of the examiner should have my 92er 4.2L an engine control lamp, but it does not glow.
I think I can remember in the dark that, in fact, before the Lambda probe was exchanged, such a tell-tale has lighted up on occasion. At that time, the car also had the notorious "wave-like" acceleration. That's all fixed now, and the box is finally running fine. And now I can't get the local "Pickerl" because the lamp doesn't glow

Well, and besides, I can't renew the registration, which is why I have to pay extra penalty fees for every extra day.

That is why, of course, I would like to have this corrected as soon as possible. I have a very useful workshop on hand, which specializes in German manufactures. But a few tips on what to do where are always quite welcome.

So ask for info, if it makes sense to disassemble the dashboard at once anyway, to get to the lamp, or if it might not be better to look for another possible source of error before.

Thank you for every relevant note!