You might try checking out your wiring harness under the VX, on the passenger side between the frame rail & the catalytic converter. My VX used to do this, usually in the winter when I went through a lot of slush & it would get VERY soaked underneath. The dealership replaced the entire harness once (under warranty), but of course the problem returned after the warranty expired. (Aftermarket warranty was good up to 100k miles) When the problem came back, I went underneath & started poking around. Turns out the harness & some connectors weren't secured & were contacting the side of the exhaust & melting the insulation. When it would get wet, then I'd get the goofy TOD lights and the VX would revert to 2WD only. (Not fun in the winter.)

Anyway, I mended the melty wires & re-secured them. Problem solved. Good luck!