I was wondering whether anybody out there could help decipher the cause/relevance/significance of the following codes that the S4 is now coughing up!!?
16815 Warm up catalyst; bank 2
P0431 - 001 - Efficiency below threshold - Intermittent - MIL O
16805 Warm up catalyst; bank 1
P0421 - 001 - Efficiency below threshold - Intermittent
18017 Crash Shut-Down Actuated
P1601 - 001 -
They have been reset, but the first two also appeared about 6 weeks ago, were reset then but had returned.
The car has no precats, second lambdas now behind main (sports) cats, and to the best of my knowledge I have not been involved in a crash

Thanks in advance to anyone who can shed some light!
Steve