1999_Audi_A6

Hi everyone,

I am new to the Audi community and I just purchased a 1999 Audi A6 with 178k miles, automatic transmission. Had the car for 2 weeks, running fine until the other day. Coming to a stop at a red light I heard a loud thump from the tranny as it was downshifting. Pressed the gas to move forward and the car barely moved forward, seems like the transmission was stuck in 3 gear. Did not downshift or upshift at all. Drove the car like this for 5 miles until I got home, turned off the car, turned the car back on and the transmission ran fine. Drove fine until the next day and it happened a second time. Frustrated I let the car sit until the next morning and it drove fine after that. Seems if I drive the car for awhile the problems happens. Any suggestion on what this may be?

4Driver4

Check and see if your transmission control unit is submerged in water. If so, take it apart and fix it; if not, pull codes from the TCU and post them.

1999_Audi_A6

I just checked and a P1857 manufacturer control transmission code came up.

4Driver4

Did you pull up the carpet and check the control unit itself.

The code you pulled is useless. You pulled it from the engine control unit. You need VAG-COM to pull the transmission codes...but only *after* you verify that the trans is dry. Do not even turn on the key until you do this.

1999_Audi_A6

Ok i will check to see if there are any water issues around the TCM unit. Thanks for this help btw

4Driver4

Make sure you open the black plastic box and check inside. Don't just peek under the carpet!

1999_Audi_A6

OK, i'll keep you posted.

RUFUSDESIGN

How do you go about pulling the carpet up? I am not in the mood to just tank it up and not be able to put it back down correctly?

beeser

That code, P1857, is rather ambiguous, likely useless and probably irrelevant. The symptoms you describe is of a transmission running on low line pressure, often caused by low fluid, a clogged filter, or both. It may be all it needs is a simple fluid/filter change. When was this last done (if ever)?

That "stuck in 3rd gear" condition is "limp home mode". This is the default when the transmission is experiencing a problem of some sort. It is accompanied by the "PRND432" indicator at the bottom of the display screen being all lit up (assuming that the display screen is still readable at all).

1999_Audi_A6

I really dont know when was the last fluid/filter change was done, i only had the car for two weeks. Usually the car runs fine in the morning but once i turn off the car the and turn it back on the issue happens. And sometimes when the car goes on limp mode, i turn off the car and turn it back on the issue goes away.