Thanks for the reply Jim.

That does leave me slightly mystified as to why the literature at Alldata should state that the EZL/AKR (injection controller) cannot store faults - note, it does (correctly?) state that the MAS (engine management controller) and CIS-E (injection controller) can store faults. Is it possible that it depends on the age/model of the car - i.e. version of EZL/AKR unit, or are they simply misinformed (I thought their info came straight from Merc HQ in Germany)?

The reason for my visit to the garage was to try to fix an ongoing intermittent rough idle problem that seems to be very common on the M103 and M104 engine. Needless to say the CKS sensor replacement hasn't solved it! Based on what you said, might that point to the EZL/AKR unit being the root cause of my idle problem, or do you think a potential memory fault (storing #17 needlessly) is just a small 'characteristic' of my unit that I should live with?

Cheers,
Neil