Hi I had a check ad blu car will not start in 500 miles warning - counting down and the engine management light also - I topped up the ad blu - it didn’t need it - but now ad blu warning comes on and then clears once I go in to check it ( just select the message ) and it’s now measuring fine - no count down message anymore - but engine management light is still on - I have it booked in for diagnostics at Mercedes dealer - do you think this could just be an update required to clear the engine management warning - I have my mot booked same day later on so this will fail if they don’t clear the message or fix it if it’s a genuine issue ? Car is 2018 e220d cabriolet ( 29149 miles)