Audi B5A4 1.8T Transmission Multifunction Switch Replacement Writeup
 

Standard disclaimer: This article is for informational purposes only. Use at your own risk.

My problem started when I noticed my car failed to engage reverse or show R selected on the instrument cluster, even though the reverse lights came on. Other oddities included slow gear selection display and incorrect gear display on the IC, e.g. R = N, 2 = N, and 4 not working at all. What also made this problem difficult to diagnose was the lack of limp mode or even fault codes being stored by the TCU or ECU.

There are a couple DTC's that can be stored for this problem. However, they are not always present when the MFS fails and are mentioned only for reference purposes:

P0706 / 17090 - Transmission Range Sensor Circuit Range/Performance
P0707 / 17091 - Transmission Range Sensor Circuit Low

Following this guide will help you fix this problem and save hundreds, if not thousands of dollars in repair work.

Length of procedure: 3-5 hours depending on skill and problems encountered.
Difficulty: 5 of 10, but prior transmission mount replacement knowledge helps with this procedure.

Parts, supplies, and tools needed:
01V-919-821-D - Neutral safety switch/MFS. Fits all B5A4, C5A6, and '97-99 A8 years. $500 list, ~$360 @ www.genuinevwaudiparts.com. This is a dealer-only part, so don't waste your time at Autozone or the like.
10, 13, and 15mm 3/8" sockets
¼" T-27 Torx socket driver
8mm Hex-head 3/8" socket driver (purchase new for this job!)
17mm crescent wrench
3/8" Ratchet driver
3/8" Socket swivel joint
10-12" 3/8" Socket extension bar
Channel lock pliers
Small pry bar (optional)
2 x M6x10mm Hex bolts
PB Blaster
CRC Electrical contact cleaner
Dremel rotary tool with cutoff wheel (optional)
Zip ties

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The new MFS:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0317.jpg">

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0318.jpg">

Before installation, zip tie the plug end of the new MFS on both sides of the rubber grommet. This should hopefully prevent contact corrosion from happening again. While not pictured, I also repeated this step on the harness end on the car's wiring.

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0323.jpg">

Start your replacement by safely supporting your car with jack stands and properly supporting the transmission so you can remove the mount. Also disconnect the battery while you are working and do not reconnect until you are finished.

Removing the belly pan is required and the metal strip the rear attaches to is recommended. The metal strip is held on by two 10mm bolts. Removal of the front left wheel is also needed to access the bolts holding the mount and transmission bracket. Because of this, use of Rhino Ramps is not recommended.

Locate the wiring harness connecting the MFS to the TCU. It is located front left of the transmission under the axle shaft:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0320.jpg">

Disconnect the wiring harness and inspect for damaged by coolant leaking from the oil cooler and/or coolant flange. Mine was salvaged using the CRC cleaner:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0300.jpg">

Remove the two bolts on the bottom of the transmission mount with the 13mm socket driver. Then use the 17mm crescent wrench on the bolt head and 15mm socket driver on the nut to counter the removal of the center bolt:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0324.jpg">

Use the ratchet wrench, 8mm hex drive, 3/8" extension bar, and swivel socket to remove the three bolts that hold the transmission bracket on. These bolts are sealed with thread locker and make an audible "pop" when the seal breaks. Because of the amount of torque it takes to break the bolts, use of a new 8mm hex-head socket driver is strongly recommended. It will help reduce the chance of stripping the bolts and causing further delays.

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0321.jpg">

When the transmission bracket clears, you will have a clean shot of the MFS in all its glory. Removal of the two T-27 Torx bolts is all that is required. They are <b>NOT T-25 Torx bolts</b>. If you use a T-25 driver, you will strip the bolt, then be removing the threaded part with channel lock pliers. Make sure to soak the bolts with PB Blaster first:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0329.jpg">

Before removing the MFS, note the clock gear position on the MFS so you can align the new MFS's. Be gentle and pull it off evenly so as not to damage the clock gear drive.

With the MFS removed, you can clean the clock gear drive up a little, but do not attempt to turn it by hand:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0331.jpg">

Using the T-27 driver, the right bolt still stripped because of corrosion even with a healthy soaking of PB Blaster. I had to use the Dremel and cutoff wheel to remove the bolt and then a pry bar to break the corrosion bond with the MFS. I ended up with this:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0333.jpg">

I soaked the threads with PB Blaster then used the channel pliers to spin it out of the hole without any damage to the transmission-side threads.

Install the new MFS by first aligning the clock gear to match the original then up with the gear drive. Gently press, but <b>DO NOT FORCE</b> the new MFS on. Instead of reusing the terrible Torx bolts, I used two M6x10mm bolts from Home Depot. They're not as long as the original Torx, but they're long enough to support the MFS. Thread locker can also be used, but is not required.

New MFS and bolts installed:

<img src="http://i7.photobucket.com/albums/y293/FastA4Turbo/audi/IMG_0334.jpg">

Reinstallation from here is reverse of removal. I used the good `n tight torque spec because I did not have factory specs handy at that time. Another disclaimer: factory torque specs are there for a reason.

Good luck!

add it to the faq

Already did. Kris will be adding it to the tech section too.

Well done Nate. Very professional IMO.

Thanks! It was a bit of a chore, but saved sooo much money doing it myself.

What was the quote you got? If you got one at all?

I did not. I estimate the cost to be...
 

$470 MSRP for the part + 25% markup = $590
$120/hr labor x 3 hours = $360

Total: ~$950 at the dealer.

Hi Nate,

thanks for the informative post, I had "pro's" fit my MFS but it isn't working propally. I have now decided to do it myself. When 'P' is selcted it shows 'R' before going into panic mode, same for 'D' and '4'. you said in your post to 'not turn it by hand' could it be installed out of alignment and if so how do I ensure that the switch and shaft are aligned? or do I have other problems here (maybe a bad connector to look for?)

any advise is appreciated

Rick

97 a4 auto
 

the gauge cluster that show the gears, p,r,n,d,4,3,2 doesn't show up when i switch gears. every gear works fine but when in reverse it acts as if it s in neutral it just revs when you give it gas. i have never worked on a Audi but it seems to be the multi function switch... wo i be correct with this guess???

Thanks a lot Nate. I am in the process of changing the MFS myself and I must say that I am able to do it only and ONLY because you have posted up those pics and detailed notes on tools etc.
I have one thing that is still bugging me though. When taking off the MFS, you said be careful of the position of the gear. But that gear has a flat part and the rest with serrations. So, you can really not mess up because the MFS itself has a flat part and serrations so that flat goes on flat and serrations on serrations...I am just checking this in case I might end up doing something crazy!

Tx

Bix