Jaguar XK 2008 - Wont Start - Kill Switch
 

My Jaguar XK of three trouble free motoring years suddenly decided not to start.
The doors unlock and lock, headlights are strong, battery voltage fine, fuses ok, etc, etc.
Here are the symptoms: With foot on brake pedal, push start button, central console dies, interior ceiling light turns on, a tick tick tick from engine bay.
Had vehicle transported to dealer who after running diagnostics says car has been modified with a "kill switch" which they can't find but have disabled - yes explain that logic.
Anyway, has anyone experienced similar Wont Start symptoms as mine and or know of a kill switch modification and if so what is / where is it and how is it user activated and can it be removed?

Your symptoms are the symptoms of a battery failing under load, and nothing else. How old is the battery? Has it been tested under load? This is a typical fail pattern for modern batteries: the lights and horn work but ask the battery to power the starter and it collapses!
I dealt with this exact pattern of behaviour in an XK two weeks ago...and, yes, it was the battery.
Before you do do another thing, settle the possibility of battery failure. These cars need full voltage all the time. And it is good to remember Occam's Razor: the simplest answer is usually the correct one. Here, it is the battery.
The correct battery for your car is a group 92 battery...and remember this: new batteries are never fully charged despite what the shop will tell you. You need to start with a battery that you KNOW is fully charged; otherwise you run the risk of never having a fully charged battery if your normal use pattern is short runs and/or infrequent use...and then you will have electrical issues of one kind or another.

Yes, it's the battery
 

I agree with SOV211.
A jump-start from another battery would be enough to prove that there's no weird "kill switch". The dealer didn't tell you if they tested the battery?
I had one vehicle that did this intermittently. I changed the battery and it still got problems. Each time, I would jump start and it would be fine maybe for a day or two, maybe not! I went all over that car for months trying to look for parasitic currents etc. and found nothing. Finally tested the new battery at a car parts store and it was bad! That's what I got for buying lower priced batteries at a well known low price store.

When you do get the new battery, CHARGE it before you install it. With a GOOD charger. Over night, if not for a complete 24 hours. Disconnect it once and let it restart after it first 'finishes'. It'll charge some more.

Press the START button BEFORE you put your foot on the brake pedal. It'll start quicker, with only a tap of the brake pedal.

Yes, I know that the Owner's Handbook says the opposite, but trust me it works. Inadvertently stepping on the brake pedal repeatedly ("pumping" the brakes) makes it much harder to start, and you have to really stand on the brake pedal.

Try resetting your battery car's electrical system. Remove both positive (+) and negative (-) cables and touch the clamp ends together for a minute to discharge the capacitors. Before putting the cables back on, connect a digital voltmeter to the battery posts and measure the voltage. If it's below 12.5 vdc, it's weak and you need to charge it overnight. You'll probably also need to reset the windows. For details, see: https://www.jaguarforums.com/forum/x...adings-113258/

THAT sounds bad! As per your quick description, someone may try to short out the BATTERY side of the cables.
While the actual narrative was correct, that first little ditty sounds Not Good.
Maybe instead say "Try resetting your car's electrics"???

Hello All - thank you for your responses, it tremendous to find such interest, support and useful information.
I guess I failed to say in my initial description that I too suspected the battery which is why I;
1. Charged the battery to full with a 16 amp charger - still the same symptoms.
2. Tried jumpstarting from another of my vehicles - still the same symptoms.
3. Called roadside assist who put their super powerful external charger on to jumpstart - still the same symptoms.
4. Had the vehicle towed to the Jaguar dealer who gave me the Kill Switch modification story which I suspect is just an excuse for they can't locate the cause.
So, if anyone has any further thoughts they would be sincerely appreciated,
In the meantime I'm off today to collect the XK and pay a very expensive bill and to keep my fingers crossed that this does not happen again.

ok confusion on my part but is the car running now? If so what did the dealer do besides tell you about some kill switch.

I'd want to chat with the service tech who actually fixed your car, and not the service adviser.

The plot thickens - here is the latest after collecting the car today - it appears that there is a relay that has at some time been added to the circuitry and this failed which prevented the start signal from being send to the starter motor. The dealer bypassed this relay and all is well now. However, the dealer did not determine where the circuit went to but assumed it went to a kill switch somewhere in the car which they can't find and I know nothing of.
Rather than me trying to explain the technicalities, Im attaching the the worksheet and diagram and some photos that hopefully will mean something to someone more wise than me.
The question remains, why was this relay added to the car's circuit (assuming it was) and what did it do?
All and any ideas welcome.
https://cimg0.ibsrv.net/gimg/www.jag...642bcfcf47.jpg
No 1 - Statement of Work Done
https://cimg1.ibsrv.net/gimg/www.jag...16e239ed0d.jpg
No 2 - Mechanics Notes
https://cimg2.ibsrv.net/gimg/www.jag...5f394d8a8e.jpg
No 3 - Diagnostic Readout
https://cimg5.ibsrv.net/gimg/www.jag...722f7dd6bf.jpg
No 4 - Circuit Diagram with Offending Circuit Highlighted
https://cimg8.ibsrv.net/gimg/www.jag...ac75e03d43.jpg
No 5 - Close up of Circuit Diagram
https://cimg9.ibsrv.net/gimg/www.jag...f69165763c.jpg
No 6 - Pointing to Offending Added Relay
https://cimg0.ibsrv.net/gimg/www.jag...84e1094672.jpg
No 7 - Pointing to Offending Added Circuit

You might have a GPS tracker in the car, they often have a kill switch so you can "kill" the car remotely if it gets stolen.
Can you get in touch with the former owners?

I have a tracker fitted to mine and (as part of the security) they don't tell you were it's located.

In the event of it being stolen the tracking company can remotely immobilise the car when stationary and call the police, which sounds like what a previous owner has done to your car and the immobiliser device has somehow kicked in.

What was the final bill?

Oh and glad it's sorted now :)

Doesn't seem like it would be too hard to follow the wires from the relay and see where they take you... There you will find your switch or kill device....

Could be a lot of work depending how long the wires are! :D

The added component is clearly problematic...but I notice the multiple low voltage issues on the readout sheet...in other words, the low battery voltage may be precisely what triggered the discovery of the added component! And this would explain why after three trouble-free years of satisfactory performance the car suddenly would not start....

The XK mantra:. The many modules in these cars require full voltage to operate properly. Full voltage, no problem. Low voltage, random problems...and in this case it was a no-start condition (as it was in the 2007 XK that I dealt with recently); investigation on the OP's car uncovered the fact that a non-Jaguar accessory was connected to the system. This may be an entirely accidental issue since for 3 years this component caused no problem...now, with documented low voltage (check the sheet) the modules are not speaking to each other. If this were my car I would buy a new group 92 battery, make certain that it was FULLY charged, and install it, using a CTEK maintainer when the car is not being driven.

Hello All
Appreciate the further input and advice and yes I too think it is time for a new battery.
And now a new twist; I put the docments away in the glovebox and found among the manuals a "Jaguarwatch Stolen Vehicle Tracking System" manual. I suspect this is what the added relay and wires in the circuit can be attributed to. My plan is to see if I can contact Jaguar or whoever the current agent is for this system and see if, from the photographs, they can confirm my suspicions. As much as I would like to go on a journey of tracing wires, I am at the stage of leaving well enough alone.
Once I have a view on the Jaguarwatch, I put another (hopefully final) post out on this.
However, I do agree, keep the voltage up and all will be well, so again it is time for a new battery.

Hello All
It's been a while since I last posted on this because everything has been going fine since the "kill switch" circuit was disabled by Jaguar and I installed a new battery.
Then a few days ago I went to start and the same symptoms and before the "kill switch" circuit was disabled, namely;
1. Push start button with foot on brake
2. All electrics die with engine fault light on
3. Tick tick tick from engine (assume petrol pump priming)
In disgust, I walked away and came back the following day and tried a start again and it goes!!!!
Not wanting to have a repeat of the non-start, off to Jaguar I go to have the diagnostics read and yes they confirm "Start Button - Signal Invalid" was recorded on the date the car wouldn't start - reference attached DTC Printout which shows DTC B108A-29. However, they cannot tell me why and when I asked what if it happens again, Jaguar suggested I put the car on a truck and bring it back to them, For this service (?) Jaguar charged me $$$$$!
https://cimg7.ibsrv.net/gimg/www.jag...ac03c988ed.jpg

So, now I'm left not knowing if I have a reliable car and whether I can trust.
Any and all thoughts appreciated as Jaguar can't help I'm hoping somewhere on the forum has the required expertise to pint me in the right direction.

Try reversing the order on your step 1, and see if the problem every reoccurs, i.e. push and hold down the start button, then step on the brake. It’s the most reliable way to start the car.