Peter_98A6

About two weeks ago our speedometer gave up the ghost. No acting funny beforehand, just woke up on a cold morning (about 15 outside) and the speedo needle didn't move at all. And, of course, a cop was right at the entrance to our community, so I got a ticket two miles from our house. Nice.

The last few days the transmission has been acting funny. I started noticing it shifting harder than I wanted about a month ago, but hadn't looked into it yet. Now it shifts extremely hard from third to fourth, if at all. It seemed, on the way into work, that it was between gears pretty often (engine just revved, no power to the road). It was randoming shifting rough between second and third also, but third to fourth is almost nonexistant at this point.

I finally got my VAG-COM yesterday, which I was waiting for before looking into the speedo issue, and it gave me a few fault codes including:

16885 - Vehicle Speed Sensor: Implausible Signal
(P0501 - 92-00 - Unknown Error Elaboration)

17736 - Knock-Control: Cylinder 4: Regulation Limit Exceeded
(P1328 - 68-00 - Cylinder 1)

I thought I saw an issue on another screen related to the transmission, but it's not showing up in my logs. I'll have to grab it this afternoon.

I bought the car about a year ago with 67k miles and I'm just about to 89,500 miles (albeit a bit unsure as the speedometer's been out for a week). Could my transmission problems be due to needing a flush and new fluid? I expected that the last owner changed the transmission fluid around 45k like they were supposed to (it was an off lease two owners ago), but I suppose I have no guarantee.

What else could I look at? I'd appreciate any advice. I might end up having to take it to the shop anyway as it's our primary vehicle... I hate taking vehicles to the shop though without having a good idea of what the problem is.

SMOKIESMAN

It sounds to me like a speed sensor for sure! My wifes Town and Country van did the same thing! Was workin great and the next time no speedo and the trans would not shift up! Dealer put in 2 new sensors and works great now! Plus you got a code for speed sensor! Thats where I would put my money!

Smokie

Peter_98A6

it drove reasonably well for the last week and a half, so it seems questionable that it would suddenly start affecting the transmission.

Mr. Malcontent

at the dealer by flushing out the trans and the fluid being replaced.

vanhawk

I just replaced my speed sensor. $26 from the local Audi dealer. Suprisingly, it was alot more expensive online. It only takes a few minutes to replace. The VSS is on the transmission differential right near the drivers side front axle and right in back of the oxygen sensor. Remove the connector, spin it and pull it out. Pop the new one in and your good to go. As for the knock-control it may have been coincidence. I have been having an intermittent Throttle position sensor problem which has been giving me similar transmission problems but you didn't throw any of those codes

SMOKIESMAN

The tranny computer needs a signal from the speedo sensor to do the correct upshifts!

Smokie

Peter_98A6

Is that the only speed sensor? How do I verify that the code I got is for that particular sensor?

I thought I'd heard something before about having to tear the dash apart to get to some wiring and whatnot. I have a dash light or two that need replacing anyway, but I'd rather have my speedometer running again quickly... and if I can avoid tearing the dash apart, I'll be a very happy camper!

How much should I expect a transmission flush to cost from a shop?

stevie_bc

.. and that immediately fixed everything. No mechanical work was done. The mechanic just downloaded the software to the ECU.

vanhawk

I had the same code, 16885. The A6 has only one speed sensor(VSS) and its not behind the dash. Others have had problems with a connection behind the dash but I don't think thats your problem. One way to check if you have a faulty VSS is to check whether your odometer and cruise works or not. If they arent working when your speedos notworking then its probably the VSS. My speedo jumped for a month before it stopped working all together.

Peter_98A6

How hard is it to re-set the ECU with a VAG-COM? If I put a new VSS on myself I'm wondering if it still wouldn't work properly until the computer was smacked back into reality...