Well..... Jag LEDs may be a step too far, but.....
Following an MIL illumination on the old Jag, I have entered the world of OBD!! I bought a reader which told me that Bank 1 upper oxygen sensor was goosed. Which I duly changed and the light went away.
I also discovered the existence of sensor sockets! Which I also now own one of.
T'is blaaaaaack magic I tell thee! Summon the mob.
Old dog, new tricks.
...... who'd of thought it, eh?