Possible failure of ECU- anyone experience this?

[papadoc]

10 days ago had just started my car, drove about a block, sitting at stop light and it just dies. Cannot restart, turns over but nothing happens. Battery, gas etc. fine. Wait 30 minutes for tow, he tries to start car (as if I am a dummy) and it starts for about 5 seconds and dies again. At my indy shop, same thing; brief start, then dies. They suspect ECU and pull the whole thing to ship back to APR. They replaced their chip, though their diagnostic did not indicate a problem but they thought perhaps it had loosened and said they upgraded the chip at the same time (though I have had it since they first came out with it, did not realize they had an upgrade). Back in the shop, same thing :-(. Car starts, runs fine, and as soon as it starts to warm up, it dies. Won't restart until it sits and cools off for a while. APR and Audi Tech Services are stumped but agree that it is probably something in the motherboard of the ECU with a failure that kicks in once the warm up cycle is finishing. It's a cool $1154 for a new ECU, which then has to go with the car via tow to dealer to inactivate the immobilizer codes, then pray it starts and hope to ship back to APR again.
We have a saying in medicine, one never wants to be an interesting patient. Now I have an interesting problem with my car. Anyone else run into such a thing, or does anything hear ring some distant bells before we head in the wrong direction?

[na1mt]

Sounds like a crank/cam positioning sensor

[Elevens]

Sounds like a crank/cam positioning sensor

Agreed! I had a 93V8 Quattro with the 4.2L engine. It had a same problem as Papadoc, It wound up being the Crank Position Sensor. So I would say that's a good call. Hope you get it resolved..................

[10SecS4]

When the car is failing to start, which lights do you see illuminated on the cluster when you turn the key to the right without attempting to start it? If the CEL and EPC lights are on, I doubt it's the ECU.

I'm assuming you've checked the ECU for DTCs and there either were none or none that apply to your issue?

[LIRS6]

10 days ago had just started my car, drove about a block, sitting at stop light and it just dies. Cannot restart, turns over but nothing happens. Battery, gas etc. fine. Wait 30 minutes for tow, he tries to start car (as if I am a dummy) and it starts for about 5 seconds and dies again. At my indy shop, same thing; brief start, then dies.

I experienced this same behavior within the first year of owning my car (bought new) - when I described the circumstances to the dealer ... each time, start-up okay when cold, then kaput after warm-up .. the dealer spoke with Audi in Germany ; the recommendation was to replace the wiring harness, which they did. Cured the issue.

Oh, and yes - same experience with the tow operator!

[as350]

Sounds like the crank position sensor. Other Audis that are of similar vintage are starting to run into almost identical failures and replacing the sensor cures the engine failures.

[kevin]

We had a car in the shop a year or so ago with an APR tune. It ended up someone had inadvertently enabled the immobilizer that came with the APR tune via the switching system they use on the turn signal stalk.

[papadoc]

Very much appreciate the input and good wishes. I have great faith in the guys in the shop I use, and have relayed this information on to them. Awaiting word back. Getting a bit tired lugging around in a big old Yukon XL...

[lswing]

Very much appreciate the input and good wishes. I have great faith in the guys in the shop I use, and have relayed this information on to them. Awaiting word back. Getting a bit tired lugging around in a big old Yukon XL...

Why not drive the Bugatti?

[ttboost]

His neighbor won't let him anymore...

[papadoc]

Why not drive the Bugatti?

Would if I could! Believe me though, that is not one to use as a daily driver...

[na1mt]

Update???

[papadoc]

Had to wait for the crank position sensor to arrive, not available locally, should be installed tomorrow. Hoping that this does it!

[papadoc]

Groan. Replaced the crank position sensor, no change. The car starts in the morning and runs fine until the warm up cycle is complete and then dies. Won't restart until cold again. I don't want to have them replace the entire ECU at $1200 unless I really know that will do it, but wow, this is frustrating...I've suggested as noted above that they call Audi in Europe. Still in the Yukon...

[10SecS4]

Did you check for boost leaks?

[papadoc]

Did you check for boost leaks?
Don't know that they have, but again, it runs fine until it doesn't! Always after warm up. Each morning they start the car, drive it into the bay, and it dies. No codes either. Possibly going the route of our colleague on Long Island next.

[10SecS4]

A boost leak on a mass air equipped car like the RS6 can result in the condition you're describing. Do you smell fuel at all either while you're cranking it or as it's running before it dies?

[ttboost]

Coolant temp sensor?

[Chung]

A boost leak on a mass air equipped car like the RS6 can result in the condition you're describing. Do you smell fuel at all either while you're cranking it or as it's running before it dies?

If that is true would an error from the MAF reading also cause this? Combining yours and LIRS6's suggestions it could be the MAF wiring (though this should be easy to check with VAGCOM)? I had to replace my MAF wiring but the failure was just no boost.

And since we are grasping as straws are you sure it is not that your engine is too small and you need to see if a larger more powerful engine will solve the problem?

[hahnmgh63]

Did your shop ever Vagcom the car for codes? Any OBDII code reader should be sufficient since it is an engine/drivetrain related code were looking for? Without running codes its a hit and miss shot in the dark. With that said, what about the DME relay/fuel pump?

[papadoc]

Yes, VAGCOM was run, and that is the mystery- no codes thrown. My shop feels this is a failure in the ECU. Spoke with them today, and they acknowledge that the wiring harness could be bad, but the cost to do that as a guess is high- very time consuming and expensive to boot. When they test power to the leads to the ECU, there is power, but then they don't get the response from the ECU. That was their initial thought and initially sent the whole thing back to APR, thinking that their chip was bad, and they installed a new one on the ECU. That did not change the result, and before OK'ing the purchase of a new ECU, I had them try replacing the crank position sensor. So next step, new ECU. The joys of a car out of warranty...

[10SecS4]

Something here isn't adding up. If the ECU wasn't responding then they wouldn't be able to connect with the VAG-COM to check for codes. If you turn the key to the right but don't try to start it, are the CEL and EPC lights illuminated? If so, I really doubt it's the ECU. Typically when there's a botched solder EPROM solder job or the ECU is fried, you won't even be able to connect with the VAG-COM. If you have the APR chip, have you tried switching programs and then starting the car? I'd try the stock program, race gas program etc and see if there's any change.

[papadoc]

When the key is turned to the right, the CEL and EPC lights come on but only very briefly and do not stay on as they should. Yet the car will start, but only run briefly. I thought that if it was the ECU that it wouldn't start at all which is why I had them try the crank position sensor first. APR had installed new chip and it is still in stock mode as far as I know, and the problem persisted. They also noted when the first had the car, before sending the whole ECU back to APR, that when they started the car and shook the ECU, the car stopped- which is why their first thought was that the APR chip or solder job on it went bad. When APR had the ECU, their tech said they "noted some loose leads and some that looked questionable", but they had no way to simulate running a car with the ECU in place. Tech support at Audi NA also suggested that the problem could be in the ECU.
And not completely true that no codes were thrown, as I look back over my emails. Only one that was relevant:

Inst cluster - 3 faults
Key signal too low
Contact ignition switch short to ground
Engine control module no communication

So that is the next route. Really appreciate the input from all.

[MaxRS6]

...With that said, what about the DME relay/fuel pump?

+1
and fuel filter

My less than .03 worth...

[SYNCRORS2]

Going back through the history of my RS6 Avant, it has had the engine ECU replaced.

There isn't any info on what the issue was, just that it needed to be replaced.

MG

[LIRS6]

Any resolution to the problem?

[papadoc]

Any resolution to the problem?

Yes, finally, and just today! Tried a number of the suggestions here without success, and finally ordered a new ECU which had to come from Germany. Was installed and brought to the local dealer to undo the immobilizer code, and the car is running again. Was in fact something bad in the ECU. Now shipping it back to APR to reflash and hopefully next week I'll finally be back on the road. It will be nice to get out of the Yukon XL, but I have to say people get out of your way when you merge lanes in that thing...

[lswing]

Great to hear!...you can get out of the way and ahead now. I often wonder what other drivers think when you start merging at 50, then are at 90 in 3 seconds...

[LIRS6]

Great news! A happy camper again