Well I've got my sensor now. Worked out it was the upstream one just before the cat on the manifold. It's all corroded, the plastic has all crumbled away. Disconnected it and confirmed that the sensor with the intermittent reading was then reading maximum oxygen (because it's disconnected) so I know its that one (sensor 1). Sensor 2 is just before the expansion box.

For some reason its started to get dark much earlier so fitting it will be tomorrow's job.

 

Thanks I was thinking of getting something like that anyway with it being a new car.
Should it have a new fuel filter and / or service first?

 

Always better to have a service done. But just bang some in the fuel tank.

 

Fitted the new pre cat lambda sensor and so far all is good. The old one was black and all the plastic was crumbling away.


No codes have come back on and there's a definite performance improvement too. Cant believe how aggressively it revs up and accelerates with my foot flat down!