2017 Audi A4 Ad Blue fault - P21CA Reductant control module supply voltage

Investigating & Fixing a fault on a 2017 Audi A4. P21CA reductant control module supply voltage fault stored in engine & reductant ECU. Fault relates to a corroded reductant tank ECU New Genuine reductant tank ECU Ebay - https://ebay.us/ooVLJd Check Euro Car parts for parts - https://tidd.ly/3lIO7xA Check GSF Car Parts for parts - https://tidd.ly/359Cie3 Check out the Diagnostic machine that I use: Topdon Phoenix lite 3 - https://diydaly.co.uk/products/phoenix-lite-3 Budget EOBD scanner - https://ebay.us/zVNaLk Check out some of the tools I use on a regular basis: Milwaukee 3/8” Impact driver - https://ebay.us/1BsLXo Milwaukee 1/2” 18V Impact driver - https://ebay.us/YjaEXy Milwaukee 3/8 battery ratchet - https://ebay.us/PvIW7L Milwaukee 3/8 long neck battery ratchet - https://ebay.us/EOTyZ3 Socket set - https://diydaly.co.uk/products/premier-soc... Sealey Inspection lamp - https://diydaly.co.uk/products/rechargeabl... DISCLAIMER: Links included in this description might be affiliate links. If you purchase a product or service with the links that I provide I may receive a small commission. This doesn't affect the price you pay! Any Donations to help Support my Channel are much appreciated. Donate via Paypal - https://paypal.me/diydaly If you found this video useful, please Like Share and Subscribe to help grow the channel, and never miss any future content. https://www.youtube.com/user/gavdaly?... Please also check out my website - https://www.diydaly.co.uk where you'll find top quality goods, tried, tested and recommended by actual mechanics.