Would a bad o2 sensor cause check engine light on in a 2000 XJ8?

 

Yes.

 

Thanks

 

So would lots of things - read the codes.

 

Oh yeah, the OBD said it was a faulty O2 sensor. I was just wondering if that was what was making the check engine light go on.

 

Oh. Yes it will, for sure. Everything involved in emissions must be working.

 

So, it didn't give me any more codes, but if Cat and Evap are failing, the light will come back on?

 

The MIL will only come on if the car can tell what's wrong - which may be impossible if some OBD monitors are unset.

Unset monitors will mean a smog fail (or the like) in many places.

If things are bad enough it will run open loop (terrible fuelling, will damage cats) or go into a reduced performance setting (limited max revs, terrible acceleration etc). You probably don't want to get anywhere near these cases.