Brake lights do not work
 

I got a strange problem. The brake lights do not work and the shifter release solenoid does not work either. Warning "electrical fault" shows on a display. First I thought it would be easy. The brake switch is known for a malfunctioning. I have removed the switch and tested it. In the neutral position the switch between terminals 1 - 4is closed and the switch betwwen inner terminals 2-03 is open. In the depressed mode it is reversed. I learned that the switch should closed the ground circuit to the stop light relay. The terminal 1 has full voltage on with the ignition oFF and loses it when the ignition is on. The terminals 2 3 4 have no readings of voltage or conductivity in either in any position of ignition. Where should I look?

(I also get "suspension fault" warning that might be or not be related.)

That doesn't sound right. Brake switch is normally open, brake cancel switch normally closed. There should be 12V across 1 and 4 with the ignition on (ii) until the brake pedal is pressed.

Wire colours:
US blue/slate
GB green/black
B black
WO white/orange

PG purple/green
WU white/black
https://cimg4.ibsrv.net/gimg/www.jag...820f752158.png

https://cimg1.ibsrv.net/gimg/www.jag...04eec0e458.png

That makes sense if 1 and 4 are connected together. This will normally only occur when the brake pedal is pressed. The 12V comes via the stop lamp relay, so in this state I'd expect your brake lamps to be on whenever the ignition is in position (ii). Check the relay by swopping it with one of the other brown relays in the trunk fusebox. Is the high-level stop lamp also non-functional?

Not clear at this point why the release solenoid isn't firing.

There is 12 V on pin 1 when the ignition is off. When the ignition is on no voltage on any pin. I have a whole host of electrical problems. It looks like something major.
Scanner posts these codes - P 1638, P1582 and what is worse - no communication with TCM, ABS, ACC, Instr.panel pack, ADRC and when scanner starts to scan BPM it gets stuck

Here is the info on the two codes to get you started:

https://cimg7.ibsrv.net/gimg/www.jag...7fed9ba5f0.png
https://cimg8.ibsrv.net/gimg/www.jag...19762d1c5e.png

...although if the inertia switch is tripped the car won't start?

First things first. Brake switch issues are not causing you to not be able to communicate with TCM, BPM etc. And for some reason (either the CAN network or the power to the modules), the ECM is on (which is why you are seeing codes), but it cannot see anything else. This appears to be happening on the SCP network too (BPM) suggesting the INST doesn't have power or its cables have been disturbed. The SCP and CAN networks originate and communicate in the INST.

A couple of things you could do with a multimeter before you proceed to investigate if its power is getting to the INST.

A.
1. Check the inertia switch in the driver side fascia fusebox. Try to reset it by pushing down firmly on the rubber on the top. If it clicks, that might improve things.
2. Measure resistance across the CAN network pins on the OBDII port (pins 6 and 14, see below). Should be around 60 Ohms.
3. Measure resistance across the SCP network pin to ground on the OBDII port (pins 2 and 5, see below). Should be between 90 and 150 Ohms.

B.
At this point, if 1., 2. and 3. are good, you are going to need to figure out what's happening between ignition and INST. Does the instrument panel display lights when you turn the key? Do they turn off when you turn the key to on? is the odometer always displayed (i.e. when you open the door, does it turn on and stays on when you turn the ignition to on)?

Of course, if you already know that the odometer turns off when you turn the ignition on, and the INST is not lit at the same time, you probably have disturbed either the ignition circuit in your brake travails or the circuit to INST (more likely the former). Back up and look at the wires you were near.

Good luck with it, and let us know what happened (along with your year/model that probably would be helpful to appear in your signature).


https://cimg0.ibsrv.net/gimg/www.jag...a71a9fbd06.png
OBDII connector diagram.

electrical/suspension fault
 

Thanks for a help. The car is 2006 XKR, VIN - as displayed in the instrument cluster - A44773. That I bought to replace my aging and rusting xk8. It was advertised with malfunctioning shifter release switch. After checking Jaguar web sites, all pointing to a faulty brake switch, I bought it and drove it without other problems 400 miles home. Problems started after I removed, checked and re-installed the switch.The warning "electrical/suspension fault" appeared and the brake lights stopped working. My scanner started to read a number of fault codes.
1.The inertia switch reset did not change a thing.
2. OBDII terminal: The resistance between pins 6 - 14 and 2 - 5 in specs /67 Ohm and 1099 Ohm/ ; ignition off.
3. still the same "no communication" response on the scanner - TCM, RCM,DDM,ADHLS -L/R, ADRC, ABS, IP.
4. when opening a door IP shows the mileage and it stays on till the ignition is turned on and system check routine is performed giving the warning (also airbag warning light is not on).
When scanning the scanner starts downloading data from BPM for about 4 minutes. At that moment instrument panel goes off - completely black. After another minute the heater blower goes on at full speed for 30 secs. When it stops the inst.panel goes alive again with the same messages. Scanner keeps "scanning" that cannot be stopped unless I disconnect it from the terminal.

Still "communication failure " with a scanner. I have checked the OBDII terminal as you suggested. The resistance between pin 6 -14 and 5-2 in specs.
wire colors differ from what michaelh writes:
1 - WU
2 - WU
3 - B
4 - OG
IGN OFF - 12V on pin 1
IGN ON - 12 V on pin 2
Stop light relay OK
when I ground 85 on the stop light relay - lights go on. When I ground OG disconnected from the brake switch still brake lights do not work. MY scanner Foxwell can read "Smart VIN" , but when testing different modules I get "no communication from TCM, ABS, SRS, etc, except when scanner starts to download data from BPM it gets stuck in "downloading" and the dashboard shows "electrical fault" message.

Thus, three problems left : brake lights and shifter lock, and OBDII communication failure.

The Instrument panel now works OK. The car starts and runs smoothly. Still no brake lights nor the gear shift solenoid working.
Brake switch sequences :
IGN OFF :
1 - 4 12V
2 - 3 0V

Brake depressed

1 - 12 V, 4 - 0V
2 - 3 0V

IGN ON :

1- 4 0V
2- 3 12V

brake depressed
1 - 4 0V
2 - 3 12V

Could it be problem in BPM?

Ah - you have '1999 Jaguar XK8 with 2001 engine replacement' listed in your profile. I took the screen snips from the 99 JTIS

The 2003 version almost agrees with your findings re wire colours, but not the pin-out numbering - reversed?:

https://cimg5.ibsrv.net/gimg/www.jag...5aff9ef419.png

This implies an open circuit somewhere along the orange/green wire. Note that the ECM receives a signal via BT11-5/BT11-8 when the brake lights illuminate, so there is a relationship to your non-functional shift solenoid issue.

Thanks for your answer. I am sorry I did not update my profile sooner. The car is 2006 XKR, VIN - as displayed in the instrument cluster - A44773 -. as I stated above.
The problem is somewhere on the route from the brake switch to the relay, but what makes it difficult to pinpoint is that the OG wire does not go directly to the relay but through numerous splitting points and connectors. What makes it even more confusing is that when the brake is depressed the switch disconnects pins 1 from 4 so there is no feed to the OG wire - +/-.
Thus, the pins numbering is a little different

2 - U
3 - WU
4 - WU
IGN OFF - 4 has 12 V and 1 has 12V a pedal depressed only 4 still has 12 V
IGN ON - 3 has 12 V and 2 has 12V a pedal depressed only 2 and 3 have 12V

https://cimg6.ibsrv.net/gimg/www.jag...6024e17134.jpg

Is there any possibility someone has repaired that brake switch module and got the normally open/closed connections the wrong way around? I would be inclined to run a test wire from the relay to the brake switch in place of the OG wire and see if you then get the brake lights working inverted.

It's not clear what you mean here - I'd expect only one pin of 2 or 3 to show 12V when the pedal is depressed.

There is only once splice in the OG wire (BTS5), and then only if you have adaptive shocks, although I agree there's some detective work to trace it. Try dibbit's suggestion of a point-to-point wire link and report back.

In practice, it doesn't really matter about the direction of the pinout reading since the switches aren't polarity-conscious.

tough time to find how to reply "token expired"
 

Hello.
i did some aditional measurements with a diconnected brake switch:
IGN OFF - pin 3 ground, pin 4 12V
IGN ON - pin 3 12V, pin 4 10 MOhms

measuring on the triggering terminals on the brake light relay?

IGN OFF 85 ground, 86 12V
IGN ON 854.7 V, 86 12V

when I grounded 85 brake lights came on and the gearshift solenoid opened the gate.
It seems to me that OG wire is broken somewhere. I have adaptive shocks, so I do not know whether I can completely by-pass OG from the switch to the relay without eliminating shocks operation.

Where is the splitter on OG wire" where should I look first?

You should look in your electrical guide for your car - all those questions are answered in there, including where the brake pedal input is connected on the CATs module (pin 26 on the module). Its easy enough to test if the CATS is working properly using a multimeter on the connecting wires to one of the shocks - you will see the voltage change between soft mode and hard mode as you brake (when the car is moving).

BTS5 is in the trunk/boot. JTIS doesn't give exact locations for these things, but it's a short run from the adaptive shock module to the trunk fusebox.

it shows all the connections between the brake switch and the CATS module so it should be possible to work out where the split is. Either way a test wire run from the brake switch to the relay will probably keep the CATS module connected, unless the fault is right at the back of the car - which would then be a good clue as to where the fault is.

Indeed: connections, yes - splice *exact* locations, no.

Partially fixed
 

Thanks again. A culprit found. The main problem was somebody who worked - and butchered - this car before me. OG wire was broken off the connector BT 1-9. Another wire connected with a crimp tube.The harness was wrapped in the electrical tape, so I did not see it till I unwrapped it. Unfortunately, it is not over yet. Now, when I turn ignition on - brake lights come on and the gear shifter is unlocked without a need to depress a brake pedal. When I depress the brake pedal, brake lights go off and gear shifter locks. Would just a switching OG and U wires at the brake switch corrected the problem or am I again for another wild goose chase?
Thanks again
https://cimg0.ibsrv.net/gimg/www.jag...58c2c4a49b.jpg

As suspected someone has repaired that switch unit and got the normally open/normally closed switched around.

If you have the switches out of the car I would see if you can swap the connections on the switches.

Edited to add: You need to swap both switches around, so 2 & 3 go to 4 and 1 and vice versa.

to dibbit : I did it and it was not smartest move. It probably killed ECU : I get P0447 and P0629 codes. Restricted performance on dash screen, a car will not start. Fuel pump fuse OK. No fuel relays in the trunk fuse box. All fuses in all fuse boxes are OK too. A scanner does not erase those codes. My worst nightmare would be fried ECU. Is there any way I can check it? That would be end for me
https://cimg0.ibsrv.net/gimg/www.jag...ac02e546b3.jpg
with this car....