Not sure about your model specifically but if the brake light switch doesnt work it cant tell if the footbrake is applied and hence wont let you take it out of park.
[edit] doh, clearly i didnt read your post properly
I know it's not the same car but a 211 has a small slot at the rear of the gearchange surround where you poke a rod (1/4") and it disengages the interlock. Does the 129 have a cubbyhole behind the gearchange?
2002 would make it an R230 - basics aside there is a known fault with the ESM - a plastic lever breaks inside. Not really a DIY job but can be fixed or a new ESM is around £900 fitted IIRC.
I know it's not the same car but a 211 has a small slot at the rear of the gearchange surround where you poke a rod (1/4") and it disengages the interlock. Does the 129 have a cubbyhole behind the gearchange?
Same on my W210, think it mentions something about this in the handbook?? It's not obvious at first, its like a small sprung loaded slot that you have to slide the cover back to access the hole if memory serves me correctly.
2002 would make it an R230 - basics aside there is a known fault with the ESM - a plastic lever breaks inside. Not really a DIY job but can be fixed or a new ESM is around £900 fitted IIRC.