Engine Warning Light / OBD

[monkeychap]

Hi All

I've got an engine warning light on. Wasn't sure if the car was OK to drive to the Audi dealer (it's still full dealer service history...) so I bought one of these:

https://smile.amazon.co.uk/dp/B081635ZLF

It's not picking up any codes. Is there something unusual about B7s that I need a different fault code analyser ?

Thanks

Ian

[DocMcc]

RS4 has 2 ECUs so maybe the error is on the second one - use VCDS to check - I found errors on the second ECU that were not on the main one when scanned.