car people: what does an out of spec lambda value mean?

[ayoub_ibrahim]

had my car MOTed today & it failed the emission test due to the lambda reading being too high.
is this indicative of a faulty oxygen sensor?
if not, what else could be the problem here?

[GNEP]

It means Half Life 2 is delayed

[Helevitia]

lol!

[Lambo-Fan]

I had a similar problem with my car some weeks ago. AFAIK high lambda readings indicate high emission values or an error with the lambda thing itself (this was the case with my car).
It "reported" high emission values (it's a certain error code) and throttled down the engine although there was no real problem (no high emission values).