Knock sensor or oxygen sensor

I wouldn't guess at either oxygen or knock sensors. In fact, they don't really have a close relationship, so I'm not sure how that guess came about. A diagnostic tool should be utilized to perform testing and retrieve diagnostic trouble codes that can provide excellent clues as to what is goin got with your vehicle. Those codes will require pin pointed testing to determine the root cause of the problem. The light coming on indicates that there are codes present and those will be essential in getting to the source of the problem. Leaving a check engine light on without repairing it can cause other extensive problems to occur. For example, if you have something going on that is causing the fuel system to deliver extra fuel to the engine because It thinks you need it -- that unburned fuel can exit through the exhaust system and burn causing the catalytic converter(s) to get extraordinarily hot, and result in internal damage to them at a very high cost. So, I would recommend professional testing as soon as possible. https://repairpal.com/repair-shops