Hi, hope you can help. Got a 2006 Jaguar S-Type, 2.7 automatic.

Issue – on occasion, the car won’t start. It’s happening daily now, after running it for about 20km or so and then trying to start it within a few minutes to an hour afterwards.
It flashes errors – gearbox fault, parkbrake fault… it just resolves itself if I don’t drive for a while, but if I have to restart the car I need to do a reset trick I learned from Youtube in order to drive. Once it drives, the cruise control won’t work till the next time I start the car.
Sometimes if I drive the car off and get a bit fast while it’s cold, it goes into limp mode.

Also, if I use the power supply (cigar lighter) for e.g. an FM Bluetooth device, within the same hour all the above happens.
I’ve researched and saw it’s often a voltage/load issue. So I had the battery and alternator checked. Alternator is OK. Battery I had to replace so it’s new.

But still happening. When replacing the battery I had the diagnostics reset – all messages seemed to relate to losing connectivity (parkbrake, gearbox, ABS, even DPF) so maybe wiring or the ECU?

(Also the previous owner was an electrician and installed a custom frontal park distance control, I wonder if he’s messed something up – as also on the (touchscreen) radio speakers the sound goes higher-lower which may be a wire, or just a crap system)

Will put in brake fluid over the weekend to see if maybe it's a legit error on the brakes at least.

 

Welcome to the forum.

Can you please elaborate on this reset trick, such as provide a link to the video? I'm curious what it entails, and if this provide any more clues.

Have you seen this thread?

https://www.jaguarforums.com/forum/s...attery-193787/

Your symptoms are a little different, but you may still find some useful info in there.

What brand is your new battery? Was the battery replaced due to the present symptoms or for some other reason? One oft overlooked function of the battery is to act as a giant capacitor to dampen normal AC ripple from the alternator. This ability degrades with age, but the battery typically dies due to other problems before this decreased capacitance is noticeable. However, our cars are more prone to this problem due to the long wire run between the alternator and battery. So it's kind of a long shot, but I wonder if a new bargain-brand battery could be part of the issue.

More reading on AC ripple:

https://www.underhoodservice.com/alt...n-the-machine/

https://www.motor.com/magazine-summa...ripple-effect/


Note how the first article talks about AC ripple causing network comm problems. Sound familiar? Might be worth investigating. You mentioned the alternator was tested. Did they specifically check for AC ripple? If not, they should have and I'd highly suggest finding a place that can do it. The test only takes a few minutes, and you can kinda sorta do it at home with some voltmeters. However, the test is much more accurate using a meter (or oscilloscope) specifically designed for it.

 

Hi. Thanks for the reply. Reset trick is here:
https://m.youtube.com/watch?v=FeufVb...bmcgcmVzZXQ%3D

I've just put new brake fluid, hopefully that might eliminate the park brake fault. But will try it out in e week.

I had a Varta battery before. Tested fine but when I turned on the head lights it dropped to 11v. New battery is a local make Willard, reputable over here. 12v 90a "568".

 

Be sure to charge the new battery prior to installation as they may sit on a parts house shelf for several months before being sold.

For all the vehicle modules to function correctly, there must be a minimum of 12.6 volts available when measured with a voltmeter across the terminals, and the ignition in the OFF position.

 

Interesting. I've never heard of that before. Not sure I understand entirely what he's trying to accomplish, though, but it does seem to have worked for you.

Don't get your hopes too high. The brake fluid level should have nil effect on the parking brake fault. The electric parking brake has one electric motor/gearbox and two push-pull cables to mechanically apply the rear brakes. Experience shows two basic faults giving the park brake fault, in no particular order. Both faults could be active:

1) Low prestart voltage: It's perfectly normal for voltage to dip under the massive load of the engine starter. Battery voltage doesn't recover immediately after engine start, and the parking brake motor struggles under load with reduced voltage. The control module may not be happy powering up with reduced voltage, too. This is the fault often fixed with a new battery.

2) Mechanical binding: The actuator gearbox and push-pull cable are prone to corrosion. This causes the motor to work harder than normal.




Where are you located? South Africa? Had to laugh at the big typo in the opening page of their website:

https://willard.co.za/

It says "...there's away" but it should say "...there's a way". And the SUV shown has a big dent at the left rear quarter panel. Neither inspires confidence...

Oh anyways, I wonder if your car may be experiencing a garden variety overnight drain, partially killing the battery. Don't judge battery charge by the performance of the starter. These cars need to see 12.6V before start, which is a VERY high standard. With a partially discharged battery, the highly efficient starter still works adequately, so it's easy to misinterpret this as the battery being good.

You can check for a drain as detailed here:

https://www.jaguarforums.com/forum/s...-drain-123535/

Another thing you can try is to hook up a battery charger every night for a week or so. That way, you're starting off the day with a battery known to be fully charged. I know, it's a pain to hook up the charger every night, but try it for a week and see if the situation improves. If so, then you know how to proceed. Won't cost anything but your time.