The common possible cause for those 3 codes per the Powertrain DTC Summary for OBD codes is a short circuit to ground in the heating or sensing circuit of the oxygen sensors. As others stated above these codes can stand for something else that makes the sensor readings suspicious to the ECM. Likely this is another clue and not the solution.

 

I tried, but it did not work.
The thing is, I thought the brake booster didn't work because of the valve. I have replaced the valve but it still only works when hot, so maybe it isn't even an air leak.

 

Threads about fuel trims explain how to tell. Or try replacing the O2s in hope. Genuine ones only.

 

I have replaced the Upstream h02 sensor in bank 1, the heating element was in fact broken. (It did not have any resistance between the 2 black cables).
The engine still runs like ****, so i want to buy a OBD2 scanner, but i dont know which one to buy. I have tried 2 cheap scanners from friends, but they dont read my jag.
The one that did work was at a repair shop when i needed to change tires. Does anyone have an '02 X-Type with a cheap working scanner?

 

I have used a generic $15 OBD bluetooth reader from Amazon and the free app Torque on my phone for many years. This reads all OBD standard engine codes for all cars made in the last 30 years. I also have a BlueDriver which is closer to $100 but reads and clears codes from all modules in the car and is more user friendly.

Many auto parts stores will read your codes for free.