This might seem a bit bit odd, but does your Multipla have a sunroof? If so, have a look at the replies to the post "leak from hatch in roof" (by Lucia).
My Multipla, although a diesel, had similar problems with the engine management and other warning lights for a long time. Various experts advised changing lots of different things, some of which I did, but to no avail.
Turns out that the problem appears to have been caused by damp in the wiring from water leaking into the panels through the 2 sunroofs. About a week after fixing this with sealant (see the post - DIY cost about £4), the engine management light faults 'cured themselves' as the panels dried out.
To date, the faults have not recurred.
Worth a try.