After removing my battery to check gearbox ecu I found this plug loose not connected to anything, anybody know what it is. I'm sure I can see another plug under the battery tray so going to remove to see it better.

It might be for a Tyre pressure sensor.

The fuel burning heater also lives under there, so could be for that if you don't have one.

It might also be for a transit relay. Jaguars have a similar redundant plug, it has some sort of relay attached at the factory to stop the battery going flat while it's being delivered, it isolates the permanent live feed i think. It's then removed by the dealer during PDI and thrown away/returned to the factory.

They are only a few guesses.

Last edited by Zirconblue on 31st May 2015 1:44pm. Edited 1 time in total

I looked to see if they could be plugged in to anything but nothing so guess they are not important. 2004 RR 4.4 V8 Autobiography

They're probably just for an option that you don't have.

Out of my guesses above, i'd say fuel burning heater, as i can't see one fitted in your pics.