316i E46 2000 M43B19 105 hp, DME Error codes 141, 171

I have 2 error codes:

- 141 - related to lambda sensor control range block (or something similar)
- 171 - is in german but the translation is something like "fuel supply short circuit"

Is it possible that the lambda sensor is generating both errors or something related to the fuel supply is generating both errors and the lambda sensor to be ok?

I understand there are 2 lambda sensors (one before the catalytic converter and one after). How do I know which one is the faulty one?

I must mention that the check engine light is on and sometimes (but only sometimes) the idle is fluctuating (600-900 RPM) and the engine seems to run in 3 cylinders (missfires?).

Thanks