Haven't been on here for a long time, mostly on Audizine but seems like no one is really helping. My car 99.5 TQM revo stage 1, test pipe(no o2 spacer), ssac exhaust. Been in limp mode for a while. I scanned it and got P0422 (Main Catalyst,Bank1 Below Threshold) and P1548 (Boost Pressure Contr.Valve Open). I bought a new N75 E valve and just installed it. Went for a test drive and in second gear seems like the turbo was stuttering but in third boosted normally(15psi). Then next day went back into limp mode again. Can it be the primary 02 sensor is out? And will a spacer help for the rear 02 sensor? HELP PLEASE...

 

Damn....wtf...no one?

 

A spacer for your secondary O2 sensor will definitely help get rid of P0422. That sensor's only purpose in life is to make sure your catalyst is working properly. I've never heard of that code putting anybody into limp mode though. You can get good spacers from RAI, 034, or eBay. I've used all three and they all work. The eBay spacer is exactly the same as 034's, just half the price. RAI uses a jetted j-bung spacer that works really well and is easier to deal with space-wise.

Primary O2 sensor could be causing you problems too, but that would likely be throwing its own code if it were starting to go bad. Have you tested for boost/vac leaks? I'm not familiar with any N7 revisions besides the "race" version, is the E valve the right one for your motor?

 

Im not sure what happend but my Audi a4 got stuck in limp mode the other day and i can not get it to go back to normal.
I have put in :
cam sensor
crank sensor
waste gate solenoid
and had maf checked.
The car only has 94k on it and i live 30 minutes from an audi dealer. The car wont go over 40 mph or over 3k rpm. traction control is on epc/esp is on as well. resets on turn off buy if i try to drive it comes back on. the battery is also brand new. Im looking at replacing the abs sensors but not sure if that will fix the issue .