Engine off, key out, open gas tank and close again. It will take ~50 miles or more for ECU to reset (if it is the gas cap, it should go away eventually). If not, reset the ecu by disconnect the battery for 30 seconds, reconnect and it should go away.
If all this doesn't work, bring them to the dealer.
Or the other option, bring the MINI to the shop that can read the code and see what it says. Mach V should be able to check the code and clear the light.
Hope this help.