SLK 280 Engine diagnostic alarm

[HeolBwr]

Hi, can someone give me the likely causes of the yellow engine diagnostic alarm. Its been up for a few days but this morning when I took it for a service and parked on a hill the garage says there was no light and they have put the diagnostic tool on and say they found nothing ??

 

[Larkone]

There should be some stored codes to interrogate but failing that wait for it to come on again and get the codes read then - STAR is your best bet.