Diagnostic socket S430

[V8Rumble]

Started the S430 today and as I was driving it felt like it was only firing on four cylinders but picked up at 3/4 throttle, After stopping and restarting all was okay which I put down to the rain and damp(old school I know) so my question is where is the diagnostic socket so I can check any code errors?

 

[candi]

under dashboard on steering wheel side behind little flap

 

[V8Rumble]

Many thanks for the reply I will look later.