I can not hint for the ECM question but I tested my microswitches and thought they were working. Then I re-tested but pushed the lever that the brake pedal pushes on harder to it bottomed out on the switches. Than I noticed that one of them was intermittent. Pushing on the switch levers in a "normal" manner did not show that but pushing with the extra force did show it.

Dan

 

​​​​​harnes fron ​​Brake switch goes under carpet ovet the cardan tunnel, there's a sharp metal seam at drivers footwell. Mine had wire broken there yellow/something. Made new wire from brake switch to passenger(right) a pilar harness joint.

There has Been similar stories here - mine is onlyone with solution.

 

Thanks to the people who document what happens to them, thanks to them we can others follow in their footsteps.

The same thing has already happened to my xk8 from 2004. I have disassembled everything as stated in the thread (easy) and replaced the micro contacts with OMRON D2HW-A211D (desolder and solder on the board) and put it back in its place. box; So far everything is simple. The difficult part, as narrated, is to put it back (I was lucky and did it the first time, but I left the stick to hold it and I had to repeat, and I was less lucky). I have removed the seat, I have lain down inside the car, I have put a light on the outside above the holes to see clearly the only one visible (the one below), I have held the brake pedal with a fixed wrench (16 -17) fitted into the lever and into the bodywork, when I placed the switch I put a stick (about 50 cm, which I forgot the first time, so the initial success was zero) to hold it to the floor of the car , I went outside and put the nuts on (fixed to the socket wrench with a piece of paper, so that they wouldn't fall off), I gave them a little thread locking liquid (I had the feeling that they were loose when I took them off, perhaps tightening them would have been enough, I recommend checking that the two nuts are tight, as this may be where the fault comes from.) Put the seat back (I took advantage of it for some repairs, such as the control box, which breaks due to the fastening screws and it is convenient to clean the inside and apply contact protective varnish). Finally, everything works again.

Compared to other contacts on other vehicles, it is clear that those on the xk8 are very weak and that sooner or later they must be changed.

Of course, I recommend using the same board to solder the new contacts. I think that purchasing a new set, if you have the skills to desolder and solder, is no better solution than putting in new contacts.
Everything is to keep the xk8s that remain in circulation.

 

Definitely worth reusing the board and just swap out the switches...saves $$$. It's a bear getting it back in, but sure is a nice feeling when you engage the cruise control and it actually works!
I had a few sets of the switches floating around, as I had to buy...think it was a total of 10. Wish I knew where they got off to..=/

 

Hello again. After more than a year, I think the problem has resurfaced. I bought a new brake light switch. After disassembling everything today, I checked, and it shows that the old switch works (which is scary now!) just like the new one. But I have a question: The lever has a sliding contact that, if you apply a little force, pushes inwards with a clicking sound; in other words, it locks into that position. Does this affect its operation? Should it be in or out? I'm attaching photos of both positions.

 

It is a 'rachet' adjuster.
You install fully extended and it self adjusts with the pedal.

 

A quick update based on having replaced several over many years on several Jaguar models . . . yes the same cam operated twin micro-switches module dates back as far as the early X308, for which we wrote a detailed R&R in that sub-forum many years ago (search on Brake Pedal Position Switch).

Aussie and NZ owners should note that replacement miscro-switches have always been available from Jaycar and its resellers. These will fit into all BPPS modules used by Jaguar since the 90s or earlier. Wires are transposed and soldered with a hot, pref temp controlled iron.

As noted by motorcarman, the ratchet cam should be reset to the extended position during reassembly.

Cheers and best wishes,

 

Thank you very much. Yes, I figured that would happen. But I didn't notice that detail last time. I also have spare switches. I hope the problem is this part and not something else, because my new symptom is that the brake lights stay on when I turn the ignition on. I'll start with the easy stuff.

 

The ratchet adjuster needs to be set if the brake lights stay on.
DON'T pull the brake pedal assy back, just let it return normally!!!!!!!!!!!!!!!!!

 

The brake lights are working fine now. I've noticed I have a habit of running the tip of my right foot (left-hand drive) under the brake pedal; perhaps this action has forced the lever's ratchet back.
But something's not right. After clearing the error codes, "Cruise control unavailable" and "DSC system malfunction" are still appearing, and the ABS light is on.
Since the scanner says the left rear wheel sensor is faulty, I'll check them all. I usually check the rear ones often because grease from the universal joints sometimes stains the teeth. Time to lift the car and start "Operation Cleaning." We'll move on to the easy stuff.

 

Indeed, the problem was with the left rear wheel sensor. The screw was more than half loose. I took the opportunity to clean (although I had already cleaned them) all the sensors and the notches on the reluctant wheels. I tightened them to the correct torque, and after driving for 10 minutes, all the warning lights and messages disappeared. I'll run a scan later, just in case there's anything left. In short, the brake switch and the sensor must have been faulty.

 

Well done....

 

Sometimes spell check by is pretty funny.

Z

 

My English is bad; I meant reluctance wheel, magnetically speaking. Clearly this is a "false friend" word. Is that what you meant? Thanks for pointing it out; I'll check the writing more carefully, but the enthusiasm of "everything's fixed"...

 

I think you nailed it, my wheels are reluctant sometimes too.

i meant spell check often changes my typing into a different meaning, and I don’t catch it.
l

Z

 

I just drove over 250 km without any problems or warning lights on the dashboard. Before heading back, I started the car, drove to my brother-in-law's house, parked, and everything was fine. After two hours, I started the car again, and shortly after beginning the drive home, the DSC message and the orange warning light appeared. After the 250 km, I parked at my daughter's house, started the car again, and there were no errors. I'll have it scanned again this afternoon. The brake lights are working. I don't know if I should suspect the brake light switch connector. The battery is 12.7 V.

 

Hello again. The scanner ran and there were no errors. I drove around town and there were no warning lights on the instrument panel.

 

Hello again. I've been thinking and thinking. Although I'm sure the brake pedal switch failed and the screw for the left rear wheel sensor was half-loosened. On my XK8, I have two sets of wheels: the original 17" and the 18" (with different rims/tires front and rear). Since I can't find 245/50 R17 tires, I've fitted 235/55 R17 "all-season" tires, which are 1.995% larger in circumference (if my calculations are correct). These tires are also larger than the 18" ones (considering the front tires are larger than the rear ones). Although a 3% error is allowed for passing the MOT/vehicle inspection, could this be the cause of the DSC system malfunctioning? and that this error manifests itself with speed and kilometers, disappearing when the speed decreases.
I might have to discuss this in another thread.

 

The larger circumference wheel/tire goes in the rear.
It is acceptable for the rear wheels to turn slightly slower than the fronts.
You run into issues when the rears turn faster than the fronts and the ASC attempts to intervene.
It determines that the rears are spinning/slipping and losing traction so it tries to compensate.

 

No, in this case, they're the same size (the rear ones are larger on the 18, 19, and 20-inch rims). On the 17-inch rims, all four tires are the same size. I put 235/55 on all four wheels because I couldn't find 245/50.