OK , procured a test harness from Mercedes , results as follows :-
Normal running , 30ma at cold start , about 1-2 ma when warm at idle, minus 5>6ma during normal acceleration , 0 > 2 ma at cruise.
(no cat on this car)
Have tried with and without the decel switch connected and the fault occurs regardless , approx -60ma on decel followed by a massive 250ma approx surge at the point the fault occurs.
After the engine cuts it is then reluctant to start , two things affect this , 1/ holding the throttle flat to the floor , the engine will then restart with some hesitation 2/ disconnecting the test meter , so effectively disabling the EHA , the engine will then immediately restart.
What do I check next ?