Can a lambda sensor be faulty with no codes showing?

[zollaf]

so its just the co slightly high, hydrocarbons and lambda are both bang on. co is probably about bang on as well, but the cats not working as well as it should. my money is on the cat. in this case i might be tempted to buy a bottle of catclean then go for a proper italian test tune, i.e on the redline as much as possible, foot down, get the cat as hot as you can to get it clean, then get it tested immediately, before it has time to cool even a little bit.

[Crasher]

It is likely that running it for a year with the MIL on has caused damage to the catalyst, that is why it is a warning light, not an advisory light. Your CO, HC and lambda readings are perfect PRE cat, with that lambda reading a working cat would, err well work!

[zollaf]

forgot the bit about the mil light being on for a year. blimey, you should have just put some tape over it like most people do.

[Crasher]

Ahh yes, the old burying one's head in the sand principle.

[flat4fanatic]

Thanks guys, advice much appreciated, cat was spot on. Now with full mot. Cat was significantly less that I was expecting too.
Light's been on since the prev owner blanked the egr, but replaced it with a good one last week so no light now.
Cant complain though, the car was a freebie off a mate.