How do I troubleshoot and repair a DTC P0020 / 17944 on a 2004 Audi S4 Cabriolet?

This code pertains to the camshaft sensor and/or a timing issue. You will at the very least need a really good scanner to look at actual values but the main tool you will need is experience with this engine. This really isn't a beginner type of issue so if you don't normally work on cars you can buy a workshop manual on your car to start learning or you can find a shop near you. Here is a link to find a good shop and a link to get a workshop manual for your car. Use this link to find one near you. https://repairpal.com/repair-shops http://bit.ly/2L2Ptj3 Alex