05 V6 S-Type owner here, and I honestly don't know why my car won't start up, not cranking, ever since I disconnected and reconnected the battery. The voltage on the battery reads 12.1v, basically a brand new battery too (about 2 weeks), and I've tried jumping to no avail. Some other problems I experienced before disconnecting is a parkbrake fault, and my a/c system screen glitching up until not even turning on at all, and my key fob not working, and I'm pretty sure its battery is okay.

I'm pretty new to Jaguars so I would greatly appreciate if any of you knowledgeable could help me out.

 

If the battery has less than 12.2 volts with the ignition in the off position and the headlamps on, the battery is suspect, regardless of age.

What is the number of kilometres/miles on the vehicle?

What is the fuel pressure at the Schrader fitting on the injector rail?

Is the MIL on, and if so, what codes are stored in the system?

 

Have you attempted to start the car in “N”? See if this helps.

Link JagRepair.com - Jaguar Repair Information Resource

 

12.1 is very low. Maybe it will recover if charged else need a new battery.