Hi Minikeefy, the fault codes give you the first part of the diagnosis, P codes are standardised accross all EOBD platforms, * it looks like you have a fault on cylinder 4 which may be an injector related issue eg, supply voltage, short to earth, open circuit for instance.
It would be worth checking the basics first, Spark plugs, HT leads, compressions etc.
At this point I see no reason to see why there is a lambda sensor fault, yes, it may be reading excess oxygen due to the likely hood of a misfire as detected by the fault code P272, Cylinder 4 contribution.
hope this may help
regards Dave
