Audi Hold Assist retrofit

[SunnyBard]

Over the course of the last week I've retrofitted the Audi Hold Assist to my car, it was one of the options I dismissed at time of ordering, thinking it would be of low benefit with an automatic. The fact that they call it "Hill Hold Assist" in the brochures does it down as a feature IMO, manually applying the electromechanical handbrake every time you stop soon gets tedious, meaning I've developed a tendency to sit with my foot on the brakes a lot of the time

Soon after I took delivery of the car I noticed that DavidB8 had a partial article on retrofitting it, but I decided to wait until I'd put the car through its first service before tinkering.

AudiEnthusiasts Hill Hold Assist Install

A couple of other useful web sites

Audi Hill Hold Assist retrofit (almost) done - Audi A5 Forum & Audi S5 Forum
Looking for crimp-on wire terminals for back of fuse block to add new circuit - AudiWorld Forums

Getting the replacement switch and repair wires was easy enough (the fuse wire certainly not cheap though) just to confirm the latest superseded part numbers, I obtained the following

1x 8K2 927 225 C WEP (this is for RHD cars)
2x 000 979 009 E
1x 000 979 025 EC
1x 000 979 023 E

Plus a few extras such as wire, fuse, sleeving/fleece tape, heatshrink tubing.

I scoured the web for articles explaining suitable routes for the extra wires, this article is actually about fitting a radar jammer, but illustrates the ECU box route (albeit on a LHD car) which I used.

DIY: Install a Laser Jammer - AudiWorld Forums

To keep things neat I decided to run the extra wires within braided "fishnet" sleeving from the centre console to the right hand front fusebox where I picked up power from a spare fuse position (I couldn't face taking power from the rear fusebox like the true factory fit) then up through the ECU box, within the trough under the windscreen cowl (past the brake servo, battery terminals and washer bottle) down to the ABS controller.

Removing the ABS plug is simply a case of sliding down the red lock and rotating the grey lever, but then there's very little slack to play with and I was a bit stumped how to open up the connector to insert the extra contacts, I found a semi-helpful German article, but still couldn't figure it out (not wanting to break anything) so put it back and left it for a few days.

http://www.audi4ever.com/forumv2/ind...c,63316.0.html

Eventually I found a Spanish article with photos that really helped with the ABS plug, again the author warned about breaking the plug, you need to register to see the photos.

Brico instalación de Audi Hill Hold Assist - Electricidad Audi A4 B8 - Audisport Iberica

Now I felt I knew enough now to proceed, and cut the tie-wrap holding the ABS wires in place, the top tab of the hood popped off easily by inserting and twisting a Stanley blade, after pulling the top of the hood forward a few mm, I could insert a tie-wrap in one side and out the other to form a handle with which to pull the hood, while inserting a finger into the bottom of the hood and levering it left and right to remove the tabs on the sides towards the bottom ... I got it off without breaking them.

Then using a pin I piggled out the rubber bungs from the holes for pin8 and pin16 (double checking the numbering) at this point looking into the holes, it became clear what the comment about the purple retaining plate meant, and I levered the two purple lugs towards the centre of the connector, this opened the holes and the repair wire contacts clicked home nicely, and I levered the retaining clips back.

The pins on the repair wires came with rubber plugs included to make a good seal into the connector

Yesterday I was ready to solder the repair wires at the switch/fuse/abs locations to my extra wires, I used heatshrink tubing on all the soldered joints and self-amalgamating tape for good measure over the joints to the ABS unit, and used fleece-tape to bind the repair wires onto the loom more neatly ... no local dealers/car parts/car audio places seem to stock it, but you can get it from eBay.

Doing the re-coding was the easy bit, with this and enabling TPMS, my VCDS has partly earned its keep.

Overall it took a bit longer than I hoped it would do, mainly due to my unfamiliarity with modern cars, lack of room for sausagy fingers, the components of the car being designed to clip and snap together easily but only come apart with difficulty. Respect to anyone stopping to take photos and write a full how-to article, it would have slowed me down too much, but I'm happy to answer questions if anyone finds this in future and has any doubts.

Finally it's so nice to see the green (P) light up when coming to a halt now, it's noticeably smoother setting off again with the AHA compared to the electromechanical brake, no more squatting down of the car due to only using the rear brakes. I can see it's going to take me a couple of weeks to remember I have it, all-in-all I'm very happy with the retrofit