today this happen. start car and drive. go to store and come out and car says no remote in car. then get out and try to lock and wont lock. get back in and it starts. did it again at next store. windows and some lights work. get the car to start and come home and then same thing. battery is acdelco pro battery not the cheapy. battery made in march 2019. what is the problem?

 

What is the battery voltage across the terminals with the ignition OFF when measured with a voltmeter? For the vehicle to function normally, there needs to be a minimum of 12.6 volts.

Many electrical 'gremlins' chased on these forums are the result of a failing or weak battery.

 

What about the battery in the smart key?
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I'd also add that I don't trust any battery, no matter how new, and I trust battery testers less, and the most unreliable thing I know is an auto parts store testing a battery.

I'm someone that throws money at problems sometimes but with batteries I buy a new one if I have the slightest doubt that's the problem.

 

If you don't drive your XJ every day for at least 30 minutes your battery isn't getting fully charged. I'm retired and the pandemic has caused me to stay home and rarely drive anywhere. I keep both of my Jags on battery maintainers to keep the batteries fully charged. I recommend the CTEK MUS4.3 for both the primary and secondary stop-start battery. Here's how to install it:
https://www.jaguarforums.com/forum/w...d.php?t=130801