Well today i replaced my rear right abs sensor as i wacked it with a hammer when i was doing the rear wheel bearing, and when i was reading through the fault codes in order to erase the abs one, 18039 popped up on the screen, i've been on rosstech's website and saw the causes, i have an other pedal but i'am clueless to what the Ecm is or where it's located.

Can anyone adivse me a good course of action ?

Just delete it and see if it comes back.

it just came back up after a 50 mile run

Any chance you wacked one of the O2 sensors? This can cause this error without giving an O2 sensor fault!!

If you hadn't been hammering the underside of car I would have suggested the following...

Using VCDS, turn the ignition on but don't start it.

Log MB62, push the throttle pedal to the stop and then slowly release the pedal until it is fully up.

MB62.2 and MB62.3 are the position sensor and one should change is the opposite way to the other. When one is at 100% the other is at 0%. The two should add up to 100%.

well i did change the wishbones and osf wheel bearing, i had to hammer a socket onto one of the wishbone bolts as it rounded, seems weird though,

theres a guy near me with vcds guess i'am going to need to get to know him, wonder many cups of tea it'll take before he helps me , think it's worth changing the pedal ? only takes 5 mins and i have a spare anyways ?