Got the XJ about a month and a half ago and the only issue I had with it was an airbag light that would stay on sometimes, and when it was on whilst driving, I had no tach/Speedometer.
Anyways, Was driving around a couple days ago, and my XJ threw a Check Engine light with a P0123 Code
So far, I've put in a new TPS to no avail, so It'll still sputter after letting off the gas, and shifts extremely hard and at the wrong points since the TCM is Receiving bad data from the TPS.

Not sure If I should replace the clockspring next and see if that fixes the Airbag light, as well as potentially fixing the P0123 Code since I've heard tell of the TPS's wiring having something to do with the Clockspring?

My horn still works and I don't have cruise, so I'm not 100% sold on the Clockspring, but it's my next course of action I believe.

 

Me, Me! I know this one....Maybe. When I modified and repaired my center console I had similar loss of tach and speedo and airbag light. I didn't have a code reader but moving the connector to the airbag made this come and go.
Hope this helps