hi the other day i was driving and noticed a yellow light on the display (looks like a gearbox) i looked in the manual and it says its an emmissions control light (used to be called an ecu or eml-engine management light), whilst i was driving i noticed the car would make a camshaft noise when driving and pressing the throttle but when i stopped and revved the engine it seemed fine (no cam noise) there is also a loss of power


1 engine light displayed
2 loss of power (may be in limp home mode)
3 when driving i get a progressive camshaft worn noise but at idle and reving its gone

could this be some type of sensor that needs replacing ? and how do i check the mil codes without any special tools or a dealer charging silly money to do.

any help would be appreciated guys . many thanks in advance.