2000 xj8. I was repairing the brake pedal switch soldering the board but I let the solder run to two wires didn’t notice it anyway reinstalled the switch so started the car took it for a drive all work well for a few miles the dash lit up like a Christmas tree. Then got car back home now I have Electric fault and Suspension fault took out switch again repaired my mistake but still have electrical fault and suspension fault did a hard reset over night still same problem did I cook the ECU if so I have another one from same year same model can I just swap it out or do I need to send the original one for repair thank you jrb53 car runs great but still have faults

 

Forgot to mention I had p1638 code

 

Well, you could try the alternative ECU and see what happens.
It could not be worse than what you already have.

 

These brake switches are still available to purchase brand new.

 

Brake Pedal Switch LNB6420BB


https://www.fcpeuro.com/products/jag...-xj6-lnb6420bb

eBay has used ones?

 

Start with the basics; check relevant fuses, switch operation, ensure low battery isn't in play, etc. Sounds more like a CAN bus disruption than "cooked ECU", you may just have a module offline causing the disruption resulting in all those fault messages.

 

The Jag Repair website is down today to get a full schematic but I have this half of the switch

Missing pin 3 and 4

The pin 1 is provided a ground.in normal operation but if power goes down that direction it would affect the SLCM

by adding power on the bck of the brake light relay you would only block the relay pulling coil from closing and should not be an are of interest.

If anyone has the 2000 wiring guide other then the Jag Repair website I can get the complete 4 pin switch and the items affected

The way the SLCM pin ST2 - 1 works is it is already putting a sensing or feeling voltage out seeking a ground through the brake switch pin 1 to 2

When the ground is found the sensing voltage goes to zero triggering the SLCM to do it's thing on the brake light aspect.

So in my opinion the SLCM has not been effected.

The other systems to look at are the antiskid , cruise control , and transmission ECU that I can think of without the complete schematic.

 

Yes, I believe my first move would be to get a known good brake switch.
Then see what if any faults remain. It is good to rule out the original
offender before pursuing wild ornithoids.

 

I agree with the above advice. New brake switch. Be sure to do a hard reset. Unhook the negative battery cable, remove the old switch, install the new switch, reconnect the cable.