Alfa Mito 1.4MA Pre Cat Lambda

[kandlbarrett]

My son's 1.4 MA failed the MOT on high Lambda. Readings were:-

CO = 0.02
HC = 5
Lambda fluctuating slightly starting at 2.32 and slowly coming down to 1.179.
The machine did not give an NOx or Oxygen reading.

EML not illuminated.
MES did not show any stored codes.
MES would not give any reading for pre-cat Lambda.
MES post-cat Lambda was not fluctuating as normal and varied slightly but relatively infrequently between 0.1 and 0.4V but mainly on 0.2V or lower.

Questions:-

1) even with a failed lambda I expected something on the graph for Lambda 1 but got nothing at all. Completely blank. Is this possible without an EML or fault code?
1) is this a failed pre-cat Lambda?
2) possibly bad connection at plush or broken wire?
3) possibly defective ECU)
4) why no codes?
5) how do I unplug that darned connection for this sensor?
Note: at the moment I can't jack the car to do this from underneath which looks like it might be easier.
6) at the exhaust the car does sound like it has a slight misfire. You can hear it intermittently fluffing though it drives normally, no misfire under load etc.
7) has this misfire destroyed the Lambda or is it possible that incorrect fuelling due to failed Lambda is causing the misfire. (Which is cause and which is effect?)
8) am I barking up the wrong tree completely?

I have checked all the vacuum hoses for leaks and can't find any.
I have checked the exhaust for leaks and can't find any.