Not sure on these but experience on Jags is this. Switch detects that the box is in the park position(normaly not tried nuetral in Jag) and then allows the sarter to engabe.Should be able to check switch is OK by removing console and pushing detent back or removing and bridge connections.Make sure box in park otherwise will move on crank and might damage box. Used as safety lock to ensure car cannot be cranked when in gear (same effct as cranking manual in gear with clutch engeged i.e will move!)