Light on after service and running rich

[e46Sean]

My partners 1.2 k12. After the service the light came on but it drove fine for a few months. Now it's started using alot more fuel, plugs are black with soot and when it was plugged in it said it was running lean, which it's clearly not.
I'm guessing a sensor is dirty/dodgy/dead and it's most likely killed the cat aswell by now.

Can anyone suggest which sensor(s) it may be and were they are on a 1.2 k12?


Thanks,
Sean

 

[gruff]

Its the rear O2 sensor mate they are the main 1s to go try that if not then check all the earths under the bonet.

Chez