Hi Darren,

I have found through experience that if the CO is above MOT acceptable levels coupled with a Lambda reading above 1.00 then it points to a catalytic converter problem. If the Lambda reading was below 1.00 as I would expect with a high CO reading then something else could be to blame. However, if the CO is at silly levels say 3 - 4%, then the cat may be faulty but there will be another fault. This is based on believing the cat will only gobble up about 1 - 1 and half % CO. This was discussed a few years ago on I think this forum and noted it to be true.

However, saying all that, I always check all the other possible causes just to make sure, but more importantly to make sure there is nothing else wrong with the management system which will curtail the life of the cat.

With regard to the Lambda Sensor waveforms, switching looks ok for a zirconia type sensor although the trough could be a bit lower at approx 0.2v. The waveform at idle is however wrong. However, I am unsure whether it is of the wideband type to which Mark alludes. Hence my question.

Hope this makes sense. I do however have the feeling that someone is going to shoot me down in flames!

Regards

Pete M