About a month ago, I asked for ideas why the ECU on SWMBOs Yaris was repeatedly flagging a small fuel leak. We were about to take the car back to the dealer, who is based a good distance away from us, for diagnosis. Mr Cheerful's tip of tightening up the fuel cap a bit more appears to have done the trick (touch wood) and has saved us a load of hassle for nothing. So thanks very much, Mr C :-)