1 cup all-purpose flour
1 ½ teaspoons baking powder
½ teaspoon salt
or
100g of all-purpose flour
5g of baking powder
I personally don't add any salt.
Either sift it all together or just stir it for a bit.
And that's Self-raising Flour, enjoy.
That's the problem now, all the electrics are a problem to fix because they are all integrated to a central computer system on the car, so most cheap fixes need the diagnostics of the main dealers to find the problem, it's OK buying new until the warranty runs out then it starts to cost.