as title says ;-)

its the engine check light that flashes mate, when you turn the screw on the ecu anticlockwise, there is also a small led on the side of the ecu that will flash the codes for you, aalthough you gotta get yer head right in ther to see it

sorry i mean does a engine management light need to be on, on the dash before codes come up on diagnostics? my bad

Are you asking if you have a fault does the warning light come on??.

sorry dude not really understanding what you mean, maybe it me. lol. Anyways, the engine check light will flash the codes at you, long flashes are the first digit, shorter flashes are the second, i.e. 2 flashes = number 2 and so forth.

faults are recorded on the ecu before the light comes on and many codes dont bring the light on !

sorry it was my english, Paul has answered my question, thanks