So this message popped up on the dash a while ago.

My iCarsoft indicated C1799, problem with the Hall Effect Sensor. As soon as I cleared it, it came right back.
Took it to my local jag guy, he thought it needed a replacement Park Brake Actuator and he fitted this
Didn't solve the problem, so I did a bit of a search here and found others had traced this code to a wiring problem, specifically the yellow/black wire which provides feedback to the Park Brake ECU from the Hall Effect Sensor in the Park Brake Actuator/Motor.
My jag guy wasn't buying this so he tried another second hand Park Brake Actuator and then a different Park Brake ECU.
Didn't solve the problem. My guy (who is a good guy and has helped me loads over the years) doesn't like testing wiring!! I did suggest it a few times....

So I got the car back yesterday and did a continuity test on the yellow and yellow/black wires between the Park Brake Actuator and the Park Brake ECU.
Yellow wire checked out OK, yellow/black did not. Access to the Park Brake Actuator connector is a pig when you've got the car on small ramps and your on your back in the garage!!
Installed a jumper between the Yellow/Black pins on the Park Brake Actuator connector and the Park Brake ECU connector, started the engine and brake warning light off, error message gone and it's asking me to apply the Park Brake in the message center on the dash.
So it was the wiring all along.

Problem solved except that now I have to install permanent jumper between the Park Brake Actuator connector and the Park Brake ECU. I have routed a new cable via the plastic grommet in the right hand rear seat and grommet under the seat next to the fuel pump access port, then along top of fuel tank with the existing loom to the Park Brake Actuator connector.
I was going to try these T splice connectors from Amazon to connect the new wire at both ends;

Anybody had good/bad experiences with them? Any other suggestions as to the best method to splice in the new wire? Access to the wiring connector at the Park Brake Actuator is challenging!!