This is regarding a 99 1.0 Lupo with the AER engine. After months of trying to fix the '00561 - Mixture Adaptation' error, i.e. the vacuum leak, I finally got it running in an acceptable manner, albeit without a steady idle. To celebrate I went for an enjoyable run up into the Highlands, returning via a 70 mph cruise down the M9. Stopped for supermarket beer and set off home. However the car didn't feel right - hesitation on acceleration. Hooked up to VAGCOM and got the 00524 error. So I changed the knock sensor, checked its terminals for shorting. There's only 2 terminals, whereas Haynes Polo wiring diagram shows 3. Anyway one terminal clearly goes to earth and the other was fine with no evidence of a short.
But the problem remains and I'm reaching the end of the road with this car unless someone can point me to the source of this error and keep this Lupo on the road.