84 Jetta GL

it's just a mileage-based counter telling you it's time to replace the oxygen sensor. Check your bentley for reset procedure (it's different for the German and American built models, yours being a Jetta is German)

nate

And just to be clear - _do_ replace the oxygen sensor now, don't just reset the counter! It's not hard, you need a properly sized socket wrench, the guts to either lean way into your engine bay or take off the inlet manifold, and the part. Dying oxygen sensors will make your fuel/air mixture go out of whack.

-A