So I, like many of us, suffer from the periodic parking brake fault that seems to appear randomly without explanation.

Many people have claimed that the parking brake fault is caused by a low battery and maybe that’s true in some cases but then again, maybe it’s not. Some folks blame it on a bad motor or cables that don’t move freely or sticky calipers etc. but there’s never been a solid answer. I dont know if a low battery or stuck cables or sticky caliper etc results in a parking brake fault appearing but knowing how electronics work, I can see why a low battery could throw fault codes for certain modules, due to the difference between analog and digital signals, and the voltage threshold‘s that digital circuits require in order to determine whether or not it’s signal is “on” or “off”

for a low voltage signal (say 5v), a digital chip might consider a voltage range of 0, 1 or 2 V as being “off” (or a digital 0), whereas it might see a signal of 3, 4 or 5v signal as being “on”(or a digital 1) for 5v input. When your 12 V battery which should produce minimum of 12.6 V is lower than 12.6 all the digital signals that are created from the 12 V battery are also reduced so if the battery voltage falls to such a level that your 5 V single is now a 3 V signal, there could be scenarios where your “on” turns to an “off” so the digital electronics sees an “off” signal when it should be expecting an “on” signal and a code is thrown. That’s why having a properly charged battery and a properly operating charging system is important because once it gets low, the effect on digital signals could cause it to throw up a code.

I can also see why a bad motor or sticky cables or a sticky caliper, could cause fault codes, but it all depends on what the fault routine uses to decide if there’s a fault or not.

Recently, i used SDD to pull my fault codes. for the most part, my car doesn’t have consistent faults, but I always seem to have a several unrelated fault codes stored, which I usually ignore but i try to clear.

sometimes they clear and sometimes they don’t and sometimes only a couple of them will clear, but at the end of the day, it’s not usually what I went into look at so I usually don’t push any further

One fault code that I seem to have consistently stored in the unrelated fault section is a “key in lock” fault code. And that code shows up usually attached to more than one module. in my case, i believe i always see the code listed for both the ignition lock and the parking brake module. Since my parking brake appears to function every time I shut the car off, I didn’t put much more thought into it but now that I’m trying to diagnose that particular “key in ignition” fault, I’m starting to think- aha possibly a correlation!

So my first step is to wiggle all the connectors and all the modules to see if that makes a difference. I look for broken wires or corrosion on connectors. After I do that, I may notice that the code clears so I think I had a loose connection and I fixed it. But then I’ll be driving along some days weeks or months later and Boom! up comes parking brake fault message on the dash.

so this week I decided to put more thought into it, and decided to look at all the electrical schematics. But when I go to the wiring diagrams i find that key in ignition signal goes to several modules. but since I do not recall ever seeing the fault code specifically identifying anything other than the ignition switch itself and the parking brake module.

So to try to figure out why I’m getting the key in ignition fault code for only the ignition switch and my parking brake module, but not a bunch of other modules , went to the schematics. But I found that because of the way the Jaguar electrical schematics in the electrical schematic manual are broken up across numerous pages, i found it’s difficult if not impossible to keep everything straight in my head to figure out what’s going on.

The key in lock signal goes multiple places through several fuse blocks and through multiple fuses in the multiple fuse blocks to multiple other modules and accessories. They even break up the ignition switch signals across several pages with only portions of ignition lock signals on some pages and it’s hard to connect everything up in my head. It’s confusing to say the least.

so yesterday and today I spent a couple of hours gathering up all of the pages of the electrical schematic manual and decided to draw it all out on a separate piece of paper. the full schematic for the key-in ignition circuit on one page was necessary for my adhd brain because I couldn’t keep it all organized in my head (and i needed to understand why I was only getting fault codes on just the ignition switch and the parking brake module. It was driving me crazy).

after i did that and looked at what i drew, it hit me. The fault does not lie within the ignition switch, if it did, I would have fault codes, pointing to all the other places that the signal goes. But I dont recall seeing other modules listed. the fault code i had specifically identifies the parking brake module,

so I bet the signal is not making its way all the way to the parking brake module or is failing within the parking brake module itself.

Now, this is just a theory at this point and more testing will have to be done to verify this. But that won’t be easy because the fault is not a constant fault. It’s intermittent, but I bet that what is happening is this- as we are driving down the road that parking brake module is monitoring that key in ignition line to decide when to apply the parking brake and it sees the key being removed. The parking brake module wants to apply the parking brake when we have shut the car off and remove the key. The parking brake module also wants to apply the parking brake in an emergency situation when the brakes fail and the driver attempts to apply the emergency brake to slow the car down as we are driving.

but what if while we are driving down the road, and the parking brake module is monitoring that signal, and there’s a momentary glitch where the parking brake module thinks we have removed the key? it is still receiving power from the ignition switch run circuit that says the engine is still running. It thinks the key is in the ignition but it got the signal saying the key has been removed. ITs conflicting data.

I bet, and this is just a theory, that the parking brake module upon seeing what it believes is the key being removed from the ignition but the car still in run mode that there must be a fault.

As far as my tiny little brain sees it, it makes perfect sense. Not knowing exactly how the parking brake fault is triggered I can imagine the engineers setting something like that up. I will try to find the fault triggering methodolgy by looking at all of my DTC manuals that I’ve collected but I don’t know if I have one specifically dealing with that fault so it might be a dead end. Hopefully, there is a manual that talks about the parking brake fault and hopefully I have it and hopefully I can find there’s a scenario where what I just stated would throw a code.

stay tuned (and please ignore any typos or voice to text translation errors that may occur in the above post. I have tried to reread it and correct them all before posting but I’m sure that I missed a few)

 

Hi
I had a friend last year in a S-type R, that kept getting parking brake fault, also a comunication fault to the epb module as well, both were completely random
turned out his was the ignition lock, his key was really lose and sloppy in the ignition barrel
we swapped out the ignition lock for a used one, where the keys was still snug and tight and the fault never returned, no more epb faults
also if I remember right on these a lot of the modules go into fault if the voltage drops below 10.8 volts, if your battery low, this is quite easily done while cranking, this is quite poor, but I assume its there to protect the electronic modules, as all the control modules on the car are solid state, so as the voltage lowers, the amps increase, I assume its just to protect the electronics
cheers
Joe

 

So it could be both. My ignition lock is also a bit loose. Somethingto look at for sure. I have a brand new AGM battery and my alternator keeps it fully charged so I’m sure it’s not a battery issue for me. My battery stays above 12.6 V all the time since I replaced the battery four or so months ago.

But my ignition switch is definitely sloppy, and if that’s the cause, it should be an easy thing to check because I just have to look at the signal at the connector going to the parking brake module

thanks for the info and sorry about the way that post was written above. I’ve gone in multiple times to correct all the confusion, typos, rambling sentences etc. but there’s no guarantee there aren’t more. It’s hard typing all this **** out on a iPhone in my brain is full of thoughts that are dying to get out on a page. Sometimes I get a little off-track.

 

exactly spot on joe. I had the same issue. The bulking tumbler also known as the little flap gets worn or bent. I bought a very good used ignition switch. Stole the tumbler and replaced mine and all has been great. The tumbler folds when the key inserted and does its thing. I also found that having the ignition key as a solo key greatly reduces the downdrop of the shank in the switch

 

Just curious, have you measured the battery voltage with the starter engaged? Under the massive load of the starter, you normally see voltage dip down around 10.5 or 11.0. Perfectly normal, not a fault at all.

You will often see the 12.6V minimum mentioned in the forum. That's prestart, with no load on the battery. (Quite a high standard, by the way) I believe that's nothing official from Jaguar, but is something based on experience. The way I interpret it, the 12.6V value is not the actual low limit by itself. It's more like experience has shown 12.6V unloaded will generally keep the battery voltage above the actual magic limit (10.5V?, just guessing) under the load of the starter. Go below that, and some of the modules aren't happy. But unless you've got a digital meter with a Min/Max function, it's kinda tricky to record a transient value where it really counts. Thus the 12.6V unloaded minimum came into being, as that is much easier to discern. That's my story and I'm sticking to it.

 

actually, I believe 12.6 is an actual limit. If my memory serves me correctly in a lead acid battery each cell contributes 2.1v. (And I just verified that it is indeed 2.1v or more accurately 2.11v. See link)Technical information on batteries)

 

Well, just like the dude said, “What I'm blathering about - new **** has come to light, man.”

so I have two keys. The original key that I got with the car which is well worn and is the one I usually used to drive with and then there’s a key that I bought and had cut myself that I hardly ever use.

well the key that I normally drive with is the one that I used to test with and got the readings above.

When I put the new cut key that I hardly ever use except for when I’m in SDD and I’m re-programming a module that requires me to insert both keys, I don’t see the voltage drop out as I wiggle it. Now mind you I’m not wiggling it like some crazy man. I’m just trying to wiggle it as much as I wiggled the original key because I don’t wanna break anything more than its already broken.



Original key on top. New key thats hardly worn on the bottom

So there seems to be a key factor involved. When I look at both keys side-by-side, I can notice that the original key that was causing the fault has much deeper grooves in the barrel of the key shank than the new key that I had cut so my question to those who know - where does the key in circuit Tumblr sit inside the lock mechanism?

Does it ride on one of these two grooves on the key in the picture? If so, I know what the problem is at least in my case.

also, interesting is if you look at the backside of the key shank it’s not grooved or worn as much as the front side, so I’m wondering if we were to take our worn keys and insert them the opposite way that we normally insert them whether or not that would prevent the parking brake fault from showing up. if the Tumblr that activates the key in the ignition switch is creating one or both of those two grooves it will have a much smoother surface to ride on - one which isn’t grooved as deeply as the other side.

I know I am a creature of habit and I always insert the key with the keypad near my thumb, so I’m always inserting the key in the same way every time, but theoretically, I should be able to insert the key with the backside of the key fob against my thumb and if the key in ignition switch is opening the circuit because the groove is causing the switch to sink lower it might not close the the switch so the system thinks there’s no key in it. If so then having the switch riding on the back side might prevent it.

I’m about to go test that theory.

Here’s a picture of the backside of my keys

once again, the original key is the top key and my new key is the bottom key

 

Waking a dormant thread...

Did your theory pan out? In the following thread, I see you added some heatshrink to the key shaft to compensate for wear:

https://www.jaguarforums.com/forum/s...around-211812/

Problem solved? If so, I'd like to add it to the Scorecard thread.

 

yes its definitely diagnosed but to fix it I need to get the ign cylinder out and repair or replace the key in switch which I havent done yet. The heatshrink helps. I took off any other keys I had on the FOB (which causes accelerated wear on the switch causing premature failure). Now if my 6’6” legs would stop ramming my knee into the fob id have no more issues.

but that was DEFINITELY the cause of my parking brake fault. It wont happen if I dont molest the fob while driving.

i had removed that heatshrink at some point. Can’t remember if it was ripping or some other reason but it was not on during my troubleshooting. Im gonna have to put some on again.

it is curious how my old original key with the additional wear on the shank definitely faults more than my new key thats not damaged. It doesn’t take much for that wear to become a problem.

 

I forgot to mention that the buzzer located in the instrument panel for the front parking aid and the seatbelt chime and the door open chimes doesn’t work in my car. I have to take the instrument panel out to figure out if I can replace that speaker/buzzer or if it’s just a wire that’s broken but I don’t get any chimes of chips or dings. If that speaker worked I imagine that I would get a chime or chirp maybe when the switch opened while driving? Maybe?

Anyways it’s on my to do list I’m just not a big fan of breaking plastic trim parts trying to remove them

 

I had the instrument cluster out on my '02 several years ago. I'm sure there are some access differences with later models, but the following thread may still be of some help. See post #24 for my experience, showing how to remove the wood trim, dash vents, etc.:

https://www.jaguarforums.com/forum/s...ype-faq-45129/

 

I have a spare cluster for an 06 str. I will look at it and see if i can get any helpful info for you including pics. They are very easy to remove if you need to. The wood trim panel unclips with an easy pull starting on the top. Then 4 screws to remove the black bezel then 4 more for the cluster. Pull it out enough to access the 2 plugins. Rotate the keepers back and the plug will follow. I will try and post something tomorrow

 

Here is a photo of the back of the clustrr. The black gizmo is the sounder. The circiut board can be removed also. It is held on by snap clips

 

Awesome I’m gonna give it a try! Hopefully it’s something that I can repair a broken side of joint or a broken wire at the connector. I know I have the correct signal being sent up to the harness on the left side of the Instrument panel but that’s as far as I’ve made it in my troubleshooting

 

Love the little mermaid! Is that a genuine Jaguar accessory?

 

my gdaughter thinks so. Carries her everywhere. Car is on jackstands right now so she is waiting

 

Well I went and done did it! And I found the problem. I had no chimes, beeps buzzes or ticks because the solder joints to the speaker were cracked. I will start a new post. Make sure you read it bc I found a major problem with my IP and its most likely a manufacturing error thats on all S Types made around vin N54100.

 

Well done! I wonder if mine is supposed to chime at anything. I’ve never noticed it

 

Pretty sure you should chime if you open the door the key in war if you have the lights on well if you have your seatbelt chime still activated which I don’t. Just polishing up the lens with some plastic polish now and I’m gonna reinstall it and hope it works. Pretty sure it will