Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
I don’t have a spare brake light switch to try, can the brake light switch cause these problems?
I have checked the earth cable both with a multi-meter and physically and can’t find a fault.It can when others can't,
It will when others won't,
It goes where others don't.
17th Apr 2024 2:44 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5068
Brake light switch is one of the many components that makes up the vehicle start protocol.
Just like the immobiliser, key code, TCM, starter relay, battery etc,etc.
It's cheap, and you should always carry a spare with you as failure will leave the car useless.
If I was a betting man my money would be on battery/earthing, brake light switch/fuse, or other systems management fuse. (eg Gateway)
If you're certain beyond any doubt there is no earthing or battery issue go through each fuse that is relevant to the start/eng & systems management.yµ (idµ - eAµ) ψ=mψ
17th Apr 2024 4:46 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 14177
M3DPO wrote:
Iid tool is showing no faults.
PROFSR G: I don’t have a spare brake light switch, I gave it away
I’m still trying to access the earth cable! - although I have tried a jump lead without success.
Many thks , Hope u get it sorted out
18th Apr 2024 6:08 am
itsaguything
Member Since: 20 Dec 2023
Location: Manotick, On
Posts: 262
After reading, from the beginning, this entire thread again I’m left wondering if the fact you have rust proofed the vehicle is just a coincidence.
No where do I see it explicitly called out that the start button was checked for proper operation.
And that we immediately went down the path that it must be the electrical system, as opposed to a component. And now leap frogging to the importance of keeping a spare module…
As a matter of process, if I suspect “components”. or a collection of, I tend to keep to the pinpoint tests from the workshop manual:
1. confirm fully charged battery. Is it fully charged now.
2. perform system reset. mandatory, if no operational responses.
3. confirm malfunctioning component. Next logical step. Have you proved to yourself the start button is good?
If 1 and 2 are still valid and/or complete, has 3 been done?
Its a matter of process… Have you looked at the workshop manual? The pinpoint tests continue.
Cheers.2015 LR4 HSE Lux Aintree Green
2013 LR2 HSE Radiance Red
2007 XKR Jaguar Racing Green
2005 XJR Jaguar Racing Green
2002 S-Type R British Racing Green
18th Apr 2024 10:29 am
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 132
Haven't checked with gap tool, is there an option to test brake switch & start switch function?
18th Apr 2024 10:25 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
Fitted new brake light switch, removed and checked start switch and still no joy, Iid tool says no faults, double checked earth cable, battery fully charged, checked all fuses under bonnet, reset with Iid tool and by connecting both battery leads together, the very first symptom was the fuel gauge just showing———— although it has fuel in.
I’ve now run out of ideas It can when others can't,
It will when others won't,
It goes where others don't.
20th Apr 2024 10:46 am
jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 769
have you checked fuses behind the glove box ?
Do you have access to live values with the gap tool ?
There might be some clue as to what module is missing if you go through them all.
20th Apr 2024 11:21 am
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
Yes I’ve checked the fuse, all good but I have not checked the relays as I don’t know how to safely.
I do have live values but without the engine running they are just greyed out.
Has anyone had a start button fail? - that is the only thing I haven’t changed.It can when others can't,
It will when others won't,
It goes where others don't.
20th Apr 2024 12:41 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5068
Unlikely as it may seem it is possible that a relay has gone bad, you could begin by swapping "like for like only" relay's in the BJB and see if you can provoke some life back into her.
Do you still have the old start button, and was it working when you replaced it?
Having sprayed wax based coatings for over 40 years without one single issue I can't see this as the root of your problem. The exception here might be if you unintentionally got some into the alternator.
This won't offer you any comfort now but at least you have a spare brake light switch.yµ (idµ - eAµ) ψ=mψ
20th Apr 2024 12:56 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
As above start button is the only thing I haven’t changed, although I have removed it and did get a continuity when pressed, everything seems to work when unlocked, screen lights up interior lights come on, foot on brake nothing, press starter nothing.
I have even put more more fuel in just in case and done system reset with the Iid tool but nothing.
I normally keep the car garaged but for the last few days before this problem it has been stood outside in the rain, I’m just wondering if that is relavent?
This is about the sixth time I’ve wax oiled including my old D3 and put plenty on particular towards the brake pipes and never had a problem till now and never gone near the starter motor, the only difference I can think of I had the Ctec charger connected this time.
I have looked at the fuel tank connection behind the near side rear wheel and it’s dry, no wax-oil on it.
Is it possible the fuel gauge sender is faulty and sending a signal to disable the engine from starting thinking it is out of fuel?- as previously stated I have put some more fuel in, but no difference and the Iid tool can reset the sender should this happen which I have done.It can when others can't,
It will when others won't,
It goes where others don't.
Last edited by M3DPO on 20th Apr 2024 3:07 pm. Edited 1 time in total
20th Apr 2024 2:35 pm
jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 769
With the gap tool, can you see the transmission in Park ?
Can you see the live value (on/off) for the brake switch ?
Member Since: 06 Mar 2017
Location: Lost
Posts: 5068
M3DPO wrote:
I have even put more more fuel in just in case and done system reset with the Iid tool but nothing.
I normally keep the car garaged but for the last few days before this problem it has been stood outside in the rain, I’m just wondering if that is relavent?
M3DPO wrote:
Is it possible the fuel gauge sender is faulty and sending a signal to disable the engine from starting thinking it is out of fuel?- as previously stated I have put some more fuel in, but no difference and the Iid tool can reset the sender should this happen which I have done.
There is something in the back of my mind about low fuel preventing start up and the culprit was in the
wheel arch connectors. I can't recall if that was a D3 or D4 but I don't want to send you chasing a "red herring", so perhaps for now it's worth just putting to the back of your mind until everything else has been tried.
The thing that I'm trying to figure out is why your ign is not coming on! If you think been out in the rain might be relevant that could be a sunroof drain issue which has caused water to get at the CJB. Is there any damp carpet on the passenger footwell?yµ (idµ - eAµ) ψ=mψ
20th Apr 2024 4:51 pm
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 132
There's a link between fuel gauge not showing and engine cutting out, whether this applies when the car won't switch on I'm not sure, just think the waxoil has got somewhere it shouldn't or you moved a cable/ connector, especially can bus, that's got an issue whilst spraying.
20th Apr 2024 10:26 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8244
No sign of moisture anywhere, I haven't removed the battery.
New brake light switch fitted and although I have 12.4v power at the plug no difference.
I have found some live values with the Iid tool and run a reset but still no joy. When I open drivers door the LR green Logo comes up on the screen.
Click image to enlarge
Click image to enlarge
Click image to enlarge
Click image to enlarge
As you can in the top left box the brake light switch is still showing OFF but the radio now plays and the clock is working without losing any time. It can when others can't,
It will when others won't,
It goes where others don't.
21st Apr 2024 12:40 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5068
So the brake light is in the "off" position even with the pedal pressed?yµ (idµ - eAµ) ψ=mψ
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