thanks for your patience, just an update.
Back at the dealer today redid all the the static tests again all passed as always (pressures, metering).
fault 121 was not present but replaced with 127, 128 still present all in active, 127 is another group fault.
techs had heard of testing truck on a hill but never done it so not really interested, we did come to the conclusion that I will go back and take a tech for a drive and try and get it to fault with him monitoring davie hopefully get to do this in the next few days as this sounds more productive than reseting and hoping it logs a fault next time.
thanks again