An indicator light has come on on the dash of my 960. I think its the lamba sensor(a little crooked 'L'). If this is the case, a: where is it, i assume screwed into the exhaust manifold, under the heat shield. And b: is there any way to test it before i replace it?

The tailpipe is very sooty as well so I assume the mixture is not right, this would point to the sensor too i think.

Tickover is not smooth and full consumption is higher than I expected.

Any help would be appreciated

Thanks

Graeme