When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
B8: Chasing Intermittent codes, CAN failures, No crank, No start. Inspect this Splice
Id like to share some information that may become very helpful later and possibly now to some as these cars become older. This pertains to B8 A4 specifically, but MAY also extend to a wide range of B8, maybe 8.5 A4 S4 A5 S5. I have yet to confirm multiple cases that is way I am sharing, hear feedback if this fixes your issues and or preventative repair prior to complete vehicle failure even driving. Verify with wiring diagrams if your vehicle wiring has Positive connection B300 located by the battery. There is also a B299 but i have not looked into it just yet. If you do or do not have problems with your car either way I'd recommend inspecting this to whoever may read this and share their findings.
First disconnect both battery terminals.
Located in the passenger trunk compartment under the taillight is a body vent. The factory body harness is secured to the floor with a clip and runs directly in front of the body vent and towards the passenger trunk fuse box. There is a 12v positive splice B300 hidden in that section of harness that is not properly weather sealed. With years of moisture, it may be prone to failure.
Locate the clip securing the body harness to the trunk floor directly in front of the body vent. Pry the harness from the body at the clips location. Carefully cut open the factory felt harness tape and unwrap the tape 2-4 inches in each direction, the splice should be close to the spot of the clip. Inside you will find B300, a capped butt connector with 3 heavy gauge red wires. Inspect the splice. You may find little or excessive corrosion or in my findings the splice will simply disintegrate. If any corrosion is present cut the 3 wires back some and strip the ends, reapply a splice joint and verify key on power, verify cleared codes and engine start!
Thank you very much OP for pointing this out!!! I had to use advanced search on google to stumble upon a ross-tech forums thread, which had a link to this thread . this information should be stickied! Causes all kinds of codes in multiple different modules including J393. You will possibly possibly pull codes such as Audi DTC 01330, 01331, 01332, 01333, 01334 and many more.
Old thread I know but I decided to check just where my car's body vents are located out of curiosity. Mine seem to be a good 8-10" above the ground in the rear quarter panels. Based on the gunge I'm seeing in the pictures, I'd be real suspicious as to whether any vehicle looking like that had been submerged in a flood.
06-11-2019, 04:00 PM
B8: Chasing Intermittent codes, CAN failures, No crank, No start. Inspect this Splice
. this information should be stickied! Causes all kinds of codes in multiple different modules including J393. You will possibly possibly pull codes such as Audi DTC 01330, 01331, 01332, 01333, 01334 and many more. 
