Vauxhall Astra engine symbol light

Make - Vauxhall
Model - Astra irmscher
Engine size/Type - 1.6
Year - 2002
Mileage - 81000

hi, my mother was driving home today, a short trip of about 5 miles. After about 1 mile the yellow engine symbol light came on and stayed on. She thinks it mite have lost power too but isn't sure. Ive checked the oil which was a little low and topped it up. We started the engine again and it started and seems to run fine but the light is still coming on and there is a high pitched constant noise coming from somewhere behind and to the right of the engine. Not very loud, it can just be heard with the bonnet down but quite distinct when its up. We gave the car a small test drive round the block and the power seems fine. Still the yellow light and high pitched noise though. Any thoughts?

A diagnostic readout by your local garage should point you in the right direction. OR, if you have a terminal in No. 6 of the diagnostic plug you should be able to access the fault code yourself by using a length of wire from terminal 6 to earth and counting the flashes on the MIL light. But you must have a terminal in No.6

thanks mate. had it read today.dodgy coil apparently.