If you have engine fault light appear on the dash you can find out what triggered the fault by reading a code produced by the ECU. You do this by performing THE KEY DANCE Don't worry you don't need to put on you dancing shoes!!
Here is how its done
Turn your key until dash lights come on then switch off
Then again turn the key until dash lights come on then switch off again
Then turn key for third time again until dash lights come on and wait,
This time you will see engine error codes displayed where your mileage was
The codes will be 4 digit codes starting with the letter P
Each fault code will be displayed for a few seconds and at the end the word "done" will come up
If there are no error codes it will just say "done"
If you miss the codes the first time, don't worry just do the dance again!
Here is a Youtube clip of the dance
Here is a link to the basic list of P codes,
If your code is not listed here please contact me with the code and I will try to help