Audi A8: Fuel Injection Error - Limp Mode?

Audi A8, Diesel, V6 2.5, Automatic.
I've been reading through the forum, but I haven't found what I'm looking for.

Error: Difficulty starting, goes into fault mode. After approximately 1 km, it restarts and everything is okay.
Off to VAG. New diesel filter and a few hoses. No improvement. The timing belt and idler pulleys are the cause.

Ab zu anderem VAG. Neue Glühkerzen, Zahnriemen verstellt. Springt sofort an geht aber auf Störung. Aus and
Turning it on only provides a temporary fix. The problem might be with the fuel injection pump.

Error memory: First comes...
00550 Injection start control 17-10: Regulation difference occurs sporadically; Readiness not available.
then, a little later.
18256 Last signal error message from the engine control unit: P1857 - 35-00.

The Bosch service can check the pump for 150 euros.
I suspect that this is also free, like with VAG. But somehow, it has to continue.
Tips are welcome.

"In principle, sticking tension rollers can cause this. Air in the system can also be the culprit. How old is the pump? If it's from around 2002 or older and has over 150,000 km, it's probably not worth checking. Eventually, perhaps this summer, the car will suddenly stop, and then the ESP will definitely need to be replaced. I'm not sure yet when the pumps actually last."

Der A8 hat 170.000 km drauf. Die Umlenkrollen und Zahnriemen sind 50.000km alt. Der Zahnriemen wurde um 3 Grad nachgestellt. After that, it ran.
He made it from the workshop all the way home without any issues. When it works properly, it runs like a charm. Is it possible to get rid of the error message?
"Does it connect to the transmission? VAG COM shows a pressure value from the ESP. I can't really make sense of it, as there's no error description."
I don't have that. Is it available for download anywhere? Also, a setting that should be at 6 is at 2. When you access the ESP controller and...
When two positions are selected, the speed remains unchanged. Then, the ESP kicks in.
Can tension rollers be "oiled"?

linden23 wrote:

The A8 has 170,000 km on it. The idler pulleys and timing belts are 50,000 km old. The timing belt... Can "tensioner pulleys" be oiled?

Why should one lubricate it? The rolling surfaces are extremely hard; if something were to wear out, a hard piece would break off and be crushed by the balls.
If a tensioner pulley (from the accessory drive belt) seizes, the engine will soon stop running! The belt will then rub against the blocked pulley!
However, they would need to make noise, as the bearings are sealed and permanently lubricated.

The Bosch service has now fixed everything. The problem was with the adjustment regulator. Since it's located inside the ES pump, the pump was disassembled, overhauled, and the electronics and belts were also replaced. Now it's working again. It was quite an expensive repair, but you have to treat yourself sometimes. (Approximately 1,000 AUD for Audi parts and 1,600 AUD for Bosch labor). Let's see if it lasts.
At E**Y in Braunschweig, there's an exchange engine available for a fixed price of 4,900 Euros. Somehow, the price seems disproportionate.