[Mannix]

Since I am considering a downpipe, I have been reading about them on the forums. I see that even some catted downpipes will trigger a code.

When a code appears, does the ECU change anything that affects the way the engine runs? For instance, some codes will trigger limp mode, right? What about the code triggered by a downpipe?

Some devices can read and clear codes. If you have one of those devices, and a downpipe code appears while you are driving, can you clear it on the fly? If so, once cleared, will it come back if you continue driving? Or will it not come back until you restart the car?

What are some of the data logging tool available? I have seen Bavarian Technic. What else is on the market?

[jb4store]

The car should not run much differently when you get a code for Cats.

The light will stay on until the code is cleared. It will take around 1-3 drive cycles for the light to come on depending on driving conditions.

There are many datalogging options that aren't BMW specific. Check out your phone's app store and you'll find quite a few cool tools.

[Walker16]

Cobb or jb4 will also be able to auto clear the code. It will be present In ecu but won't affect anything and won't show up as a ses light