Electrical fault light, get it up on mine every so often but the cars got no problems so ive ignored it. When its been on the clip it can never find any data showing it as it for some reason doesnt log it. If its after removing plastic trim around the wheel etc it could be you have tripped a fuse maybe, did you put the plugs back in correctly as they might be loose, or maybe even your immobiliser ring around the ignition barrel isnt put back on correctly.
By start up what do you mean? Is it engaging starter motor and then just failing?