Peugeot 206 my peugeot 206 1.1 petrol , has failed mot emissions only just outside permissable limits, could this be be a lambda sensor fualt?

Could be , but many other possible causes . Could check plugs , air filter , MAF sensor also .

How do you check a MAF sensor with a multimeter?

Have check plugs , all in excellent condition, air filter clean as a whistle, engine coolant temp sensor replaced and working fine

Quick way to check your MAF is to disconnect it whilst engine running . If no change in engine , its faulty

Will try that check asap, also going to check fuel return line to see if that is blocked. Failing that fuel pressure sensor?????

A mechanic also noticed fumes from under the (bonnet) hood???