Why does my car overheat,stability traction light stays on and have loss of powr

What is your question?

I have recently had problems with overheating so i have changed the water pump, thermostat , radiator and re-done the head gasket n timing chain, and now i have it all put back together i have had the stability traction light come on n stays on and have loss of power , can u please help me out? Took it to a garage and they said most of my sensors need replacing and the next step would be to check the timing chain which could cost quite abit, i have spent alot already and would like some advice please .thank you