C4 2007 BSM failure

[calebzzz]

Hi

I owe the car for 12 years, recently it shows check engine with coil circiut error. I have replaced the coil with little effect. Two weeks later car won't start with multiple faults: injectors,fuel pump, coil circuit. The only other fault I had was poor AC blower performance poor and ventilation flaps don't seem to react to control but Im not sure this is relevant.
Garage diagnosed faulty BSM and I need to find one second hand because they stopped making them.
My BSM is marked BSM-L11-00 9661682980

Question 1: Can I use different BSM, guy tells me it will work BSM-L02-00 9656086180?
Question 2: Should I investiage for reason of fault or can they just break on their own?

[wheeler]

The numbers dont necessarily need to be an exact match, if you get one of the same age & spec as your car it should be ok.
As for the failures, one way is water ingress if the cover has not been clipped on correctly but inside there are a bunch of fixed in relays that can fail over time just like any other external relay.