Peugeot 206 engine management light problem?

If the engine management light is on there is definitely a fault recorded. Either the fault has appeared after your brother has checked for faults or his diagnostic did not pick up the fault. Is he using a universal code reader? Although I have never used a universal one I do own a genuine Peugeot one and I know that they are very complex things and I doubt a universal scanner would pick up everything. For example my car reports a permanent fault with the multifunction display saying that it can't communicate with the radio, that's because I've replaced the Peugeot radio. I very much doubt a universal reader would pick up faults like that. I would get your brother to scan the car again and if he still cannot find any faults take the car take it to someone with a genuine Peugeot diagnostic or Peugeot dealer. If you're in the midlands I may be able to help.