Module question
 

On a 2003 XK8 How many or can any modules be bypassed & will the car still start & run? Specifically the seat & rear parking aid modules (water damaged)

The car should run no problem with those particular modules unplugged.

New Question: The 03 XK8 is at a repair facility & they can't get the reverse lights to illuminate, there's still no parking aid module are these two issues connected? And if so do I need to purchase a module? Speaker at rear of center console is either disconnected or the wires are broken(cars been at shop over 1 month so I can't remember!)

The yellow wire going to the parking module could cause a problem with the rear lights if the parking module is defective IF it is plugged in, but it should not cause a problem if the parking module is removed and the connector is now dry and not corroded.

If you had water in the trunk, however, the SLM (security and locking module) in all likelihood was also water damaged or at least water exposed. This module contains the sense circuitry that signals bulb failure in the rear lights. This could also be the culprit since it sits directly underneath the trunk fusebox.

First off thanks for the quick reply.
The SLM has been replaced
Will corrosion on the connection cause a problem? There is absolutely no module connected

Only if there is corrosion residue connecting it to other pin(s) in the connector or if it is still wet.

While I'm thinking of it I guess the obvious question: has anyone run into this problem or may know of another way to get it working? Won't pass state inspection without it

Try unplugging the connectors on the navigation module (assuming you have navigation) in the trunk as a test. The reverse lead also run to that unit.

The reverse lights are driven from the SLM based on mesages from the CAN bus. Are you sure you have the correct replacement SLM with the correct software loaded in it?

I don't have the Navigatiion module.
The garage is insisting that the PA module is part of the reverse light wiring,The parking aid module is: 3W83-15K866-AA, I can't find a matching prefix 3W83 or suffix AA but plenty of matches to 15K866 will any module work or is it critical to have an exact match?