DTCs - looking for ideas...

[ruxprncd]

My car generally runs very well...but I've occasionally run into overboost, and for whatever reason it feels much stronger at freeway speeds (wickedly fast) than off the line.

I found a couple of excellent posts regarding 17819/17831, so I have ideas on what to look for there. I don't think the secondary air system would have anything to do with the issues I mentioned though (?).

Would appreciate ideas on what to troubleshoot for 17865, and whether it could somehow be related to the overboost & just-ok off the line power...:vhmmm:

Here are the codes...

17865 - Exhaust Gas Temp Sensor 2 (G236): Open or Short to Plus / P1457 - 001 - Upper Limit Exceeded - Intermittent

17819 - Secondary Air Injection System; Bank 2: Insufficient Flow / P1411 - 002 - Lower Limit Exceeded

17831 - Secondary Air Injection System; Bank 1: Insufficient Flow / P1423 - 002 - Lower Limit Exceeded

17963 - Charge Pressure: Maximum Limit Exceeded / P1555 - 001 - Upper Limit Exceeded - Intermittent

[nene]

1. check exhaust gas temperature (EGT) sensors;
2. wastegate control issues, such as vaccuum line not seated properly, or need replacing;
3. check both bypass valves and lines; these are easy and cheap to replace; torn line can easily show all the codes you are getting; bad bypass valve can throw them too;
4. boost leak somewhere in the system;
5. Air Injection System leak (http://forums.audiworld.com/a8/msgs/19663.phtml); it's for an A6, but can help;

All the codes are pointing to a leak in the system. I'd check all the vaccuum lines that you can visibly see. Good luck. This is part of the love of owning a turbo charged car.
Most important, once you do find the fix/solution, post to let us know.

[ruxprncd]

Thanks Nene. That A6 link is the one I snagged a copy of last night - I think that is part of the issue. I just replaced the BPVs - these codes were occurring before then, so they didn't cause the issue (initially or now). Tomorrow I'll check out everything under the hood I can reach.

Based on the first repair manual step to replace the EGT I hope that's not the cause. That step? 'Remove engine'. I haven't looked close enough to see if there's a more creative way to solve that one.

[ruxprncd]

I found the cause of these codes:
17819 - Secondary Air Injection System; Bank 2: Insufficient Flow / P1411 - 002 - Lower Limit Exceeded
17831 - Secondary Air Injection System; Bank 1: Insufficient Flow / P1423 - 002 - Lower Limit Exceeded

The vacuum line to one of the secondary air injection combination valves was split. The proper way to fix this is to replace the line...but since I had problems getting the air filter housing off...I cut the vacuum line where the split was and re-attached it to the valve. Once I sort how to remove the air filter housing I'll replace the line.

Speaking of which...the air filter housing is attached, on the passenger side, with a bolt that is underneath the air passage. Ideas on how to remove that *&%$&* bolt appreciated! (preferably without having to remove any additional components...)

[jimmy94507]

With the vacuum line fix have you seen this DTC anymore?:
17963 - Charge Pressure: Maximum Limit Exceeded / P1555 - 001 - Upper Limit Exceeded - Intermittent

Thanks, Jimmy S.

[ruxprncd]

Just once.

I don't know if the vacuum line & overboost were related...I wouldn't think so, but with the RS6 ya never know, I suppose!