can I switch off passenger airbag?

I enquired about this before, and was told that the only way to disable it is to disable the whole system, driverside too. This clearly defeats the object.

This is only what I was told, albeit from an experiance auto-electrician, so maybe there is a way.

It's not a system with a user override, like many of the newer cars have. The only possibility is to have the airbag control module recoded with the parameters for a single airbag system, thus it will think it's fitted in a car without passenger airbag. You could then disconnect the airbag and the drivers' side will still work.

I'm not 100% if this is possible, but I suspect it should be since single airbag 8s were sold, and BMW tends to change configuration by coding rather than different modules in these cars. However you'd need access to a GT1 or MODIC, and knowledge of which part of the ZCS key (coding key) to modify. It's not really a temporary arrangement than can be switched on and off easily.

Incidentally, the airbag system in the E31 has occupancy sensors in the seats, so it should only fire the passenger airbag if there's someone heavy enough sitting in the seat. I wouldn't rely on such an arrangement with a baby seat however!

I have tried to turn off my passenger airbag for 12 years, but she keeps on gassing away in my ear....

You could try to put a by-pass switch in series or parrallel with the occupancy sensor. You'll need the wiring diagram to see what connection you need to make or break with the switch to mimic an empty seat. (The circuit probably has some way of detecting a completely open circuit- see TT's post- but it should be possible.). And, using a 2-pole switch you can use the second set of switch contacts for a warning LED somewhere.

....but you're still relying ultimately on the car's 12-year-old electronics not to trigger the passenger airbag...