Engine management light

[lilvikii]

Hi a few weeks a go, the engine light came up on my aygo. I took it to the garage and they put it on the diagnostic machine and couldnt find a fault, so they reset it and set me away. Today it came back on and they put it back on the machine and it came up with a fault code (not sure what it was) They said it could be the crankshaft or the camshaft sensor but they're not sure as they engine sounds ok, and there is no rattling. The car itself drives ok, other than the light. Sometimes when i put the aircon button on to demist the windows, the cars lights will flicker. Any suggestions? Thank you :)

[Devon Aygo]

Without the fault code it could be 100's of things, we need the fault code

[Wiz201]

my lights flicker when I put the demist fan on for a few seconds, I think that's normal. I've no other issues.