Frustrated 2004 Audi A8L 4.2L
 

Was having issues with the car missing and even stopping. Took it to two different german techs. Both said the fuel pressure was only 34PSI should be at least 50. So after about a week, after having both fuel pumps and fuel pressure regulator replaced (1300.00 later). The engine has just stop two times today. I get the follow codes with a VAG COM, never have gotten these before since I had bought the car 9months ago. Could they have done something replacing my fuel pumps and Regulator to get these codes. Any information would be helpful.
17831 - Secondary Air Injection System; Bank 1
P1423 - 002 - Insufficient Flow
17819 - Secondary Air Injection System; Bank 2
P1411 - 002 - Insufficient Flow
18666 - Oxygen (Lambda) Sensor B2 S1
P2234 - 004 - Signal Shorted to Heater Circuit - Intermittent
18663 - Oxygen (Lambda) Sensor B1 S1
P2231 - 004 - Signal Shorted to Heater Circuit - Intermittent
18847 - Oxygen (Lambda) Sensor B2 S1 Voltage too Low / Air Leakage / Sample Error
P2415 - 008 - - Intermittent
18846 - Oxygen (Lambda) Sensor B1 S1 Voltage too Low / Air Leakage / Sample Error
P2414 - 008 - - Intermittent

secondary air is going to be a vacuum leak, nearly guaranteed. O2 sensors looks to be electrical in nature, check connectors, maybe something afoul there. Lot of coincidence getting those codes after your independent was under the hood. Just sayin ....

definitely sounds like a vacuum leak. I would insect all vacuum lines for cracks or even might be one that isn't hook up. otherwise testing the EVAP since they changed out the fuel pumps, you never know. I would start with all vacuum lines first.

Also check the linkages for the intake flaps. Those are prone to break and when they do they send crazy errors. They are under the front plastic engine cover (it says v8 4.2 on it)

Thanks for all the comments. Had a smoke test today
 

from the guy that replaced the fuel pumps. Everything tested fine, really solid he told me. He said the none of the codes I returned should make the engine just stop. It has not happened since I cleared the codes, but am worried as I am taking it on a trip in a couple of days. Any other suggestions would be appreciated. Thanks

The one that comes op and just seems to leave motor erratically stopping is the crank sensor, but the codes seem like they are quite different. I suspect the codes are for other issues. Or, maybe weren't cleared? Even the codes themselves seem to fall into two or three unrelated groups.

Man have u had your turbos checked. 4.2 are natorious for turbos and pcv problems which cause the engine to idle rough and have a hard time to stay running. Just food for thought.