01N auto box problem

Hi All

New problem with the old banger.
Its a 1998 A4 B5 1.9 TDI with the 01N 4-speed auto box 275k km on the clock

Starting last week it seemed reluctant to select 4th when driving along then more and more reluctant to change gears at all. Not selecting 1st when stationary, not selecting 4th when cruising around 50mph.

Did some research and seemed to be pointing at the speed sensor(s) on the box but couldn't get it on VCDS until yesterday. (I only use the car weekends and occasionally during the week)

VCDS says its the solenoid valves, more reading on hear and other sites are pointing to a wiring problem rather than solenoid problems.


So car up on stands, find the multipin connector at the back of the box, after much swearing it comes apart, seems a bit damp inside, give it a clean out with tissue paper and a good squirt of water dispersant, dry it out again and pop it all back together. Start car, clear fault codes, run it through the gears on the slector, no faults reappear, Huzzah!!

Use the car last night, runs great, smug face engaged!

Take significant other to the docs this morning, same old problems again!!!!

So suggestions?

I think I am on the right lines with wiring but any ideas on likely source much appreciated. I thought the multipin plug was most likely as it sits exposed on the back of the box but digging into pictures at lunchtime and spares on ebay the printed circuit strip inside the box can fail? Or the cabling from the multipin plug to the rest of the loom looks very brittle and has some wicked kinks in it, a possible source of problems?

To be honest even if its corrosion in the multipin connector I cannot see how to clean it properly as its in a awkward place and very small. Imagine a 15 pin trailer power connector thats about 12mm in diameter.

Advice on the next step would be great, thanks.

Also struggling to find the part number for it as partbase says "round connector housing; no replacement part; 4-speed; automatic" Item 26 on this page
http://www.partsbase.org/audi/audi-...-cable-loom-for-speed-sensor/#p-aud-8d0972984

Hi Aragorn

Should have mentioned that I checked that already. The ECU is in the same place in the passenger footwell. All is dry in there so don't think that is the problem.

Thanks for the suggestion though.

OK update.

Haven't been able to do any serious work under the car so been doing lots of research online about possible failure points and replacement parts. (Dark at 18:30 and temps around freezing point)

Anyway whilst trawling the net I did find the following procedure to reset the gearbox ecu. Apparently it has a fuzzy logic learning system and is recommended to reset it back to defaults after doing any modifications. Anyway its free and easy so worth a shot.

Did it yesterday and after using the car afterwards and again this evening I cannot believe how much it has done. The car is completely transformed. No gear selection problems, changes through all gears with no hesitation or fuss. Appears to have completely fixed the problem. Amazed. The gear change revs are definitely different from before so I presume the reset to defaults has occurred. All I can presume is that I did actually fix the problem on Sunday but the settings on the ECU must have been confused by running it with the changing problem even for a few days.

So here is the gearbox ecu (tcu) reset procedure, lifted from a golf TDI forum:

1. Key on (dont start, just turn the car on)
2.gas down to floor for 10 sec
3.while holding gas, turn key off
4.let go of gas
5.key on (again, on, dont start) for 5 min (for throttle readaptation). touch nothing.
6.then start while touching nothing.
7.drive and see what happens.

its not uncommon to have to do this over and over, because u make small changes and forget to reset yet again. i cant count the # of posts where people change 99 things and reset 99 times, only to make one last change, forget the final reset, then give up and shoot the car with a shotgun. so for those that missed it *always reset last!*

This method is not needed for the 3speed 010, as that has no tcu and yes, this reset can be done thru vagcom too!

final note. i have done this method so many times for all my auto 4speeds, and it works everytime! if it doesnt, there is another issue that needs solving. hence, begin solving all issues my reset (easy, free, 5min). then, if needed, go to vagcom. after changes, reset. and so on until everything works perfectly. refer to my other post about solenoids and other DIYs about valve body cleaning and other issues. dont give up folks!!! usually its simple stuff to fix it.

Also need to add that when I was under the car last week I noticed that my outer CV boots have split, lots of grease still on them so hopefully I have caught the problem before CV damage has occurred. Is it possible to replace the boots with a cone with the driveshafts in situ?