BMW Repair: my eingine management light, fault number, fault description

Question
my eingine management light keeps coming on and i keep taking it to the garage to get it off again he puts the computer thing in to it but it comes up fuel or something like it i get it turned off (the einginemanagement light)and it comes back on any info would be great  

Answer
Thomas, come on man. What car are we working on? What is the fault description (word for word). What is the fault number? When does the light come on?
Engine temp.?
RPM?
certain speeds?
Time of day ?
after how many miles?
environmental conditions?
certain terrain?
certain turns? lateral forces?braking?
certain gear?
Loads on/off (A/C)?
How does the engine run? Idle? Help me help you. Put me in the driver's seat. It pays to be observant and descriptive.
-Evan