All systems go on the morning commute. Stopped for a car wash near the office, drove to office, parked. 8 hours later, suspension light comes on solid on drive home but suspension works fine. Then I notice the speedo needle bouncing all over the place, sometimes coming back to normal. Finally it just bottoms out, stops registering altogether - no speed, no mileage. Stop the car turn off. Start up, light comes back on after a mile or so, needle may or may not work but then drops down to 0 again.

WTH?? Could any of this be car wash related? I am so hoping I start it up tomorrow morning and everything will magically have gone away. Any insights? Are these two related possibly or just a really ****ty coincidence? Please tell me I am not looking at a new instrument cluster.

 

If so, you need to vagcom this to get a positive diagnosis.

I also experienced a solid suspension light and erratic speedo (actually, a dead speedo) when my speedometer sensor was malfunctioning (which happened due to a misalignment internal to the tranny).

This is the sensor that is above the driver's side front output flange on the transmission (where it bolts in). You can see this if you remove the rear part of the skidplate, and then remove the three ?5mm? allen bolts that hold on the inner CV joint heatshield. I bet that if water were infiltrating that sensor connector, a light coating of dielectric grease would help.

Alternately, you can fully remove that sensor and wave a magnet in front of it quickly, and mimic "speeds" of up to about 10MPH.

Best,
Bob

 

Perhaps a loose connection or something? What do you mean by misaligned? How is that connected to the speedo?

 

So mine was caused by my rebuild. There is an uncontained/uncaged bearing in the middle of the tranny that will basically explode if you don't prepare for it beforehand.... and I wasn't aware of it and let it explode. It's a 23 piece roller bearing. When I only found 22 pieces in the back half of the tranny, I knew I had dropped the 23rd into the front half (Front diff) part of the tranny, so I used a magnetic wand to find that 23rd part in the front half. Oops.

I now know that when I used that wand, I disrupted the alignment of the magnetic "flapper wheel", which rests (in 2 parts or "semi-circles", IIRC) on the driver's side of the front differential. To fix this, a shop pulled the driver's side output flange and that side of the differential housing, and replaced and repositioned that magnetic flapper wheel.

I actually turned this fix over to a shop to diagnose and fix, since after EIGHT SOLID DAYS of marital-stress inducing tranny removal, rebuild, and replacement, ... .... I washed my hands of my dead speedo problem that popped up when I reinstalled the tranny. These guys were a solid shop, and kept me in touch as to their methodology and the fix, so I'm aware of what was done (and I also saw the part before it was installed). They even had another allroad up on their lifts that week, and did some pretty crazy diagnostics including "slaving" the other allroad's speed sensor off my ECM, and borescoping my tranny - really good shop - some of the best $400 I've ever spent. I was actually thinking that I had stretched the speedometer sensor wire (which actually happened during the reinstall!), but this turned out not to be the mode of failure.

Aaaanyway, that same magnetic flapper wheel, when properly aligned, produces a moving magnetic field. This "pulsing" magnetic field then does one of either two things. It either opens or closes a reed switch (which is an on-off-type switch that is activated by magnetic current), or it induces current in a coil. Either way, the ECM looks at the activity in this sensor and counts the frequency of change, interpreting this as "vehicle speed". It gathers this information via the 2 prong connector in the location I previously described.

The allroad ECM uses vehicle speed for a number of purposes. It is used for ESP purposes, for vehicle stability; to tell teh suspension module when to lower from levels 3 and 4; not sure but I believe in the ABS module as one of the inputs (along with wheel sensors etc); in the overall engine management (I noticed a much jerkier ride when suddenly lifting throttle when my speedo was off); and it also is displayed in the instrument cluster. In this latter case, it is not the *direct* speedo voltage, since it is again being fed from the ECM (as a derivative signal).

So, knowing the above:

I would say, since you are seeing a solid suspension light (which asks for an input from the speedo), that your problem is likely not instrument cluster, but at the speedo itself. I am puzzled that you do not have a CEL, since mine threw one... oh yes, it only threw a CEL above a certain speed or rate of climbing speed - that's right.

So, you have "half" of my internet diagnosis.

However, if you vagcom the ECM and it shows a code related to the Vehicle Speed Sensor, you can definitevely narrow down your culprit to something either at the connector, the Vehicle Speed Sensor, or the magnetic flapper wheel inside the tranny. The connector is the easiest fix and likeliest culprit if water was involved in the heuristics/etiology of your problem.

Sigh. Hell of a long post to rouse the mind after a much needed nap.

 

Speedo worked fine entire 25 miles this morning but suspension light came back on at about 20 miles. I also notice a "floaty" feel to the handling when the light comes back on...can't quite tell if it's riding higher or not. When I got out it looked to be at normal level 2. This is definitely the weirdest AR problem I've had yet but I am nearly positive it's related to the car wash. It's not the first time I've had post car wash electronic tom-foolery. I don't own a VAG so will have to wait to read it. What chain offers free scans again? Napa or Auto Zone or something?

 

I had to run a couple of meetings in the PM while in full migraine mode, so it was good to just talk cars for a mo after work.

So....regarding code scans: you don't need an OBDII scan, you need a vagcom. I'd highly advise a Vag scan as your first diagnostic action.

 

as that is data that is sent to the suspension ECU...it is somewhat ironic and may be just coincidence but I had that happen after a car wash too...maybe due to lots of crud under there...if it is winter driving where you are with the ride height sensor wierd the car would act funny on snow/ice as the ESP doesn't work correctly...in my case it actually ended up being a ride height sensor and the suspension ECU...are you sure you are sitting at level 2? eventually it may lower once the system can't figure out what to do...just some random thoughts...good luck.

 

This is nto the first electronic weirdness I have encountered post carwash with the AR.

 

My speedomter went dead the other day and I got a 16885-bad vehicle speed sensor. I took my car to the dealer yesterday and he told me a need a whole new instrument cluster, said VSS was okay. Do I spend 54.00 for a New VSS or take his word for it that I need a new instrument cluster for $1200.00? The odometer and cruise control do not work but everthing else does.

 

first make a new post of this... you replied to a post from February