Can’t turn the screen off or on permanently. While driving it just keeps rebooting then after a few seconds of full functionality goes to black then reboots again. It’s in a constant loop of rebooting.

 

Can’t turn the screen off or on permanently. While driving it just keeps rebooting then after a few seconds of full functionality goes to black then reboots again. It’s in a constant loop of rebooting.

 

Everyone will tell you to check your battery, regardless of age. Check resting voltage at the battery terminals. Should be a minimum of 12.6 volts. Alternatively take your ca to an auto parts store and have them load test it (it's free). If it's not the battery, then this ;

It's a classic symptom of a failing module in the MOST bus fiber optic ring. The flashing symptom is the faulty module attempting to reboot. The fiber optic ring is being interrupted, There are two stacks within the ring. Trunk stack and center stack. The center stack is the stack of modules under your touch screen. They include the touchscreen, the ICM which is a gateway between canbus and fiber optics (so they can speak to each other). That's the little black box on top of the CD player. Then there is the CD/radio Player. If you have premium audio, there is also the amplifier under the carpet in the passenger footwell.

In the trunk there are a stack of modules. Bluetooth module for you phone, The Navigation DVD module (maps) if you have satellite, that module, your iPod module. BT, satellite and Navigation are the usual suspects. You need a fiber optic bypass loop. Simply disconnect the fiber optic line from the module, pick one at a time, and connect the bypass loop to the fiber optic line. Turn on your car, if the problem stops, you found your offending module. If not, reconnect it and move on to the next one.

 

MODS / ADMINS...
Please delete this duplicate thread!

 

Thank you so much! I’m thinking that the upholsterer may have disturbed something in the trunk when he replaced the back window…

 

Unfortunately they deleted the post containing the answer to my question. Not sure how I ended up posting a dupe, sorry

 

When the upholsterer replaced the rear window is there a connection in the fiber optic loom front to back that he could have disconnected? If so, does anyone know the routing? Is it just one bundle from the boot to the front?

 

Short answers...
1. there is no need to touch any harness/cords when fixing your window.
2. as they were D*(&^^&*%g around with the car, the battery was undoubtedly depleted.
3. (And the first step to troubleshooting in the manual) This is a common outcome of a depleted battery. Confirm the battery first before diving down all the pinpoint tests.

Cheers

 

Yeah, he disturbed the battery's charge by leaving doors and lids and boots open for extended periods. Same thing happens during a thorough car detail.

 

The other thread is still active, it's right here:
https://www.jaguarforums.com/forum/x...ooting-293901/

 

So if the battery is good will it just recharge from driving and then sort itself out?
12.6v standing correct?

 

Makes sense, but never any issue starting. When I opened the boot lid the black luggage flap was flat and rolled back (convertible ) so something was done. Talked to the upholsterer and he confirmed the only wiring they touched for the repair was the heated window connector.

 

No! It would take a few hundred miles of continuous driving to charge to a good level.
You need to have it fully charged with a battery CHARGER, not a maintainer or 'trickle' charger. A 10 amp or higher direct charger set up overnight would do the job. Most decent auto parts stores will fully charge a battery to test it, but that again will probably be the next day with them having the battery there.

 

Starting takes like 12.0 volts, just turning a motor. All the electronics REQUIRE 12.6 volts or they get wonky.

 

Wish I could double or triple upvote this as well as the poster, @Sean W . This is the type of knowledge that will help keep our (aging) Jags on the road. I know Sean has helped me with this exact issue in the past (I even bought a loop online and used it.)

 

@alanroberts50 , although I have not personally used it, there is a built-in self-diagnostic test procedure for the MOST Ring. See my posts HERE and HERE. Simply remove and reinsert Relay #2 in your Auxiliary Junction Box to initiate the self diagnosis. Please let us know if it works for your case.

 

@KurtC I think that initiates the test but you need SDD to tell you where the break is once the test is initiated. It's a good test if connected to SDD but I think the loop is easier, at least in the trunk stack.

@Speedmaster you are too kind.

 

Thanks, so where does the test result display? Is there a way I can combine that test with my icarsoft LR2 scanner?

 

. No you need SDD for the relay triggered test. Start in the trunk. Disconnect the Bluetooth module and connect the bypass to the line. When you turn on you car the telephone tab will be grayed out. If the flashing screen stopped you found the culprit. If not , connect it and move to the next module. It’s almost always the but, satellite or navigation but could be any of them.

 

I have had the identical fault which everyone said was the battery and it was. New battery and works perfectly. Having said that you could try disconnecting the battery touching the terminals together and then re connecting. It might work