HiI have an error on my 2006 X350 2.7; "Parkbrake Fault" pops up and the car won't move.

I disconnect the battery (battery is good) and then the fault clears. A while later it's back again.

It was happening once a week or so but now it's happening several times a day. It is annoying to say the least!!

Thought it might be the control unit (?) Any ideas on what to do would be greatly appreciated 👍🙂

Thanks
Andrew

 

After disconnecting the battery do you do the parkbrake reset?

 

Keep the park brake off by pressing the chrome button

every time you remove the key from the ignition.

Temporary fix

 

For what it is worth, I apologize in advance for a lengthy story but it might be relevant.
I just overhauled my rear power distribution fuse box this weekend by fully removing it, separating the circuit boards and replacing all four system relays, as one relay had obviously developed a continuity problem that a previous owner's auto electrician decided to bypass in every way possible by tapping into other lines to repower rear tail lights, high-stop.
I didn't know this had occurred until I went hunting for why my front seat heaters were not working - traced through and discovered the cause and the subsequent "rats nest" of a questionable professional invader.....sighhhh....

The reason I mention this is that when I reinstalled the rear power distribution fuse box and reinstated the original factory wiring integrity, I climbed into the car and wanted to test that all the tail lights were working (post rats nest removal).
Cue getting the wife involved as the rear light spotter!
I never started the car, just operated park lights, brake lights and rolled the ignition on to allow indicators to work....getting the cheerful chirp from the other half as she verified each light for me.
I then decided lastly to check that the reverse lights were also working, so foot on brake pulled gear selector out of park into reverse, then back into park - only to hear that I was too fast (not the first time I might add ) she didn't get a chance to see the other side, so back into reverse selection again ....thinking nothing of it......wrong.....park brake error came up. Never had that error before (but this car is very new to my garage).

Started car and could not move, could select any gear but car firmly held insitu.....park brake holds pretty well :-)
Thinking the worst (having read quite a few threads recently as I try to build up my knowledge of this model) I had that horrible sinking feeling....what have I done.
From the highs of fixing the relay issue for good and solving harness infractions, I was now dejected ......I decided to stop and went in for lunch and contemplate the situation.

I decided I needed to verify the parking brake module, saw in the schematic there are two power supply lines into it, one of which is derived from the rear power distribution box I had just worked on. Successfully verified both 12v supplies were present (Phew) by measuring into the back of the plug connected to the park brake module (located behind the rear electronics module in RHS rear inner guard void), the two Brown/white stripe wires had power.
Decided that the parking brake servo motor must have become out of sync with my relatively quick gear shifter movement, but it wasn't clearing itself once it was in the fault state.
Either I needed to disconnect the battery to reset car (don't have the owners manual so don't know the radio code yet if I need to reset it, an information gap I hope to solve shortly), so thought I would just disconnect the parking brake module (two connectors) to see if just that module alone needed to be reinitialized.
Short answer to a long story (sorry again for those losing the will to live) ....yes. interrupting power to just the parking brake module cleared that error and allowed the park brake servo to rehome itself and for me to start and move the car, but it did prompt me to go through a foot brake and park brake sequence to verify operation.
Been three days of back and forth driving so far without any recurrence of that error.

The take ways from this.....
Never underestimate the ability of an auto electrician to disguise a fault and effectively set a trap for you.
Don't be too quick moving the gear selector in and out of park as the servo motor might get out of step.
Wives make good spotters when it comes to verifying some of your repairs. (is the indicator working yes...no ...yes...no.......I jest)

 

Yes every time I go through that procedure.

I have noticed that the error always occurs along with a stuttering ignition...maybe a wider electrical fault(?)

 

Are you getting any error codes that might suggest an intermittent CAN bus comms error to any module(s)?
Park brake module shares direct linkage comms with air suspension and both fed out of instrument cluster, but TCM and ECM are at the opposite end of the CAN bus chain.
Certainly a CAN bus fault could manifest to produce both of your symptoms, I would expect a lot more symptoms throughout the car's systems. Either way there should be code evidence that might help narrow down the culprit.

Land Rover Discovery's will commonly throw a park brake error after start up if the battery is getting weak, is it possible you might be having similar scenario?

 

My car needs a battery. If it sits for a few days (it's not my daily driver,) I occasionally get a "Cruise not available" on the dash, and would also get "Unable to release parkbrake" if I hadn't already gotten onto the habit of overriding the parking brake by pushing down the handle as I remove the key. The first time I saw 'Unable to release parkbrake" I was not at home, and couldn't get home! Searching the forum on the phone was no help, and I forced the car to back up and pull forward several times, and the brake finally actually popped and released. Whether it broke something at that point, I really didn't care, and the message changed to "Unable to set parkbrake." Again, I didn't care.

FF a few days and I encountered the reset-everything-that-isn't-right process of disconnecting the battery cables and touching them together momentarily. After reconnecting, I was prompted on the dash to do the parkbrake reset, and I found that my auto-close didn't work on the windows anymore and learned how to train that back in. (Simply hold the switch down for 5 or so seconds after closing the window.) I expected to have to do that with the sunroof as well, but it auto-opens and auto-closes just fine after a battery reset.

The "Cruise not available" message only happens if I don't touch the car for several days, so I'm pretty sure it's just that the battery is OK, but marginal enough to have slightly low voltage after sitting a while. It doens't take much low to make things weird in this car!

Once in a while I forget and allow the parkbrake to set, and et the "Unable to release" message next time I start the car. Do the battery thing and all is well.

 

Thanks so much. I had the battery replaced last year so I'm not sure it's that.
It doesn't throw a code either which I thought was odd. There are other recent niggles - the air suspension takes a couple of minutes to engage after startup (always used to be immediate), parking sensors recently stopped working. I wonder if it's all related (?)

 

Hi Mark,
Excellent news about the rear distribution box. I had much the same issue with the engine one. When I got the car it was getting Restricted performance alerts. After some investigation, in seems one of my PCB relays died, which killed the supercharger coolant pump. Brilliant previous owner/mechanic/electrician had run an extra feed to..... the auxiliary heater pump! Well they are similar looking, but it had no effect on the RP errors. I suspect the previous owner gave up trying to fix it.

 

Check integrity and connection stability of fuse 32 (5A) in front passenger fuse box.....it feeds a minor 12v supply into both your parking assist module and also parking brake module.
If fuse is loosely fitted or fractured, you might have both problems.
Sorry...it has no tie up with air suspension with that fuse though.

 

Hi Pete,
Yeah....I ended up cutting each pin mid-way with fine side cutters and once I had the halves separated then extracted each pin remnant out of the PCBs.
Arghhh......104 pins in the rear power distribution module assembly, so 208 square pegs factory forced into round holes to remove!

Once I had replaced the relays I then replaced the pins with new ones I made from 1.5mm brass rods.
The soldering was a pain....ended up improvising and two heat sources as the heat dissipation of those large copper pads etched into the PCBs was immense.
I had my trusty old Wella 40 watt iron which just didn't have enough guts, so used my paint stripper gun to preheat area enough to allow iron to get flow going with the aid of a good solder flux paste.

Didn't want to trust trying to just butt the old pin halves together and bridge gaps with solder. If one of those joints fractures with heat or vibration, it would be a heck of a intermittent fault to find again in a year or two.
If I were to try that method, I would sleeve the severed pins with some fine copper or brass tubing so they were mechanically robust once resoldered.

 

Hi Mark,
That's what I did too, getting some of those pins out was a bit interesting, even with a good desoldering tool. I used some large diameter bare copper wire cut to length for each pin.
Pete M