yep you can, I had the same problem but no light, my lamda sensor (10 year old by the way) was reading 1.27 @ 2450 rpm, and should have been between 0.97 to 1.03. I found a hole in mine and fixed it myself.
you can check it yourself by jacking up the car, sticking it on axle stands, get under it while it is running and feel around it for leaks, it will be like a fan blowing air.
this means you save yourself a few quid.