continued:

I don't know whether your key is the same as mine.

I also have a connection under the hood of my car that allows the use of a booster battery. It is a post to which one attaches the lead from the positive post of a booster battery. The ground lead or cable from the booster battery can be attached to the manifold or any other appropriate ground under the hood. Maybe your car has the same feature.

I don't know much about SLs. I just thought your car might have these features, because they are two model years apart.