2004 XJ8 I left am inside light on for 2 days by battery was dead. The battery is a 2014 it’s stamped we tried jumping it off with a jumper box with no luck. I heard clicking in floor board. A friend csme with heavy duty battery. It final jumped. Since then I have had check engine light on the cord we’re saying it misfired on cylinders it turns over and finally starts. We thought fuel pump. Replaced map Still ids rough. I read your post here. I’m thinking I need a new battery and to reset something. Anyone can help pleade

 

Rhonda, yes, from the sounds of things, doing a deep discharge of the battery like you did hurt it. So, in short (without getting to technical) is that the battery is not filtering the voltage in the car well enough and this is causing the computer to see strange inputs. As a result, you are getting these random codes. If you want me to explain it in a lot more detail, I will.

In short, you will need to go to the store and buy a new battery. Have them install it (unless you can yourself). When they go to install their "memory maintaining box", ask them not to connect it up. This will clear all the codes in the engine computer. Replace the battery. The big trick is you need to connect the positive post first and then in one motion, attach the negative post. You don't want to have the post hit, bounce, break connection, land again, make connection, fall off, break connection, etc. You want it to touch and remain in contact. This will minimize potential damage to the computer. From there, get the car put back together and take it for a 15-20 minute drive. You want some of the time for in town driving (to get some coasting and braking) and you want some time up at say 60 mph constant speed driving. This will run the car through all the tests that it needs to do to get you back to a normal P1111 code (this is what you should see when the car is running normally). If you still have a code, then we have other issues.

 

Rhonda, if you're going to be a regular contributor, it will be best if you post in the correct forum for your car which is an X350 built 2003-2009. You might also care to get this thread moved there too.

Hope you get your problem sorted out soon

 

Welcome to the forums Rhonda,

I've moved your question from X351 to X350 forum. This is the place to post questions about your 2004 XJ8.

Graham