The check engine light is on and the car is now hesitating. on 1994 Toyota Land Cruiser

I thought it may be an exhaust leak as there was a hole in one of the exhaust manifold pipes. I repaired this but is still hesitating and the light is still on. Could an oxygen sensor be causing this?

Asked by for the 1994 Toyota Land Cruiser
This in not likely to be from an oxygen sensor or an exhaust leak. You need to read the diagnostic codes from the engine control module. There are hundreds of possible codes so guessing without reading the codes is useless. Get a hand held scanner, or take it to a shop and get the codes read out, then look on this chart for a brief description:
Post the code here and someone can give you some more info too.