Park brake fault

[goldy1]

Two in a row within a week. just had a park brake fault on my S-type EPB stuck on, I managed to drive the brake on and off by connecting 12 volt supply direct from the battery, proving the motor was working. A replacement control module got the brake working again.

Having just taken my XJ 350 off sorn I had the same park brake fault message show but this time the park brake won't come on.
After disconnecting the battery which I understand resets the system, then turning on the ignition with your foot on the brake pedal then operating the park brake switch to recalibrates the parking brake. ( not sure if this is correct but following advice on a site)
This made no difference however, I found that with my foot on the brake pedal and operating the parking switch the motor drives the brake on & off with no problem, but if I take my foot off the brake pedal and use the brake switch it just makes a beep and the motor doesn't operate.
I have tried a replacement control module that didn't make any difference (This was a second-hand one which I,m told was working but of cause can't be guaranteed )
Has anyone had this problem or knows what else can be checked, the car is a low milage 2005 XJ8 LWB

[PaulGover]

There's a known problem with damage to the wiring somewhere where it passes through holes in the metalwork. You can get shorts and/or open circuits. AFAIR there's also a possible problem with a bad splice somewhere in the loom causing open circuits.

Have you used an ODB-II reader? The EPB has messages which might help (though mostly they say the EPB is implausible). Otherwise the workshop manual basically says unplug the loom at the appropriate connectors and check for continuity and shorts to earth. You obviously know your way around this lot if you've replaced the control module.

[goldy1]

There's a known problem with damage to the wiring somewhere where it passes through holes in the metalwork. You can get shorts and/or open circuits. AFAIR there's also a possible problem with a bad splice somewhere in the loom causing open circuits.

Have you used an ODB-II reader? The EPB has messages which might help (though mostly they say the EPB is implausible). Otherwise the workshop manual basically says unplug the loom at the appropriate connectors and check for continuity and shorts to earth. You obviously know your way around this lot if you've replaced the control module.

Hi, Paul Thank you for your reply, I don't have any reading equipment, but if you say EPB doesn't really help I don't really want to go to the expense of getting a reader I wouldn't really know which one to get and I believe I would need to spend £100 + at least. (and would I use it very often)
It sounds like a difficult job just locating the connectors, is there anywhere I can download a WS Manual? also have you any idea of the most likely area to start checking the loom? of cause, it's always the last one you check.
Thanks again Dave

[iRS]

Hi Goldy1, I have experience fixing the EPB, I did write an article for the magazine, but its yet to be published. I've spent a few miserable hours with my head under the rear subframe. There are 2 electrical connectors, one is between the car's loom and the sub frame loom and the other is the connection between the motor and the sub frame loom. On some cars this sub frame loom isn’t secured properly and then I assume it falls on to and drags on the drive shaft resulting in failure. Then someone comes along and spices it back together and then that splice fails sometime later. You only need to be concerned that there is conntinunity from the plug in the boo to the motor and it sounds like you have that as the EPB does appear to work in some circumstances. I posted something on here a little over 2 years ago on how to operate the EPB from the boot connector by applying 12v, you should try that to satisfy yourself the wiring is good. I think if I remember correctly I attached a wiring diagram for that bit of the wiring, so that might help you. Good luck!

[goldy1]

Hi IRS
Thank you for the info on the wiring, once it drys up outside I will try and take a look under the car at the loom.
Just wondering if it could be the parking brake switch or wiring to it shorting?
I am confident that the wiring to the motor works as you can drive the motor on and off when I lightly apply the footbrake and use the park brake switch.
Regards applying 12 volts I did this procedure on my S type by unplugging the plug from the EPB and applying it to the lines to the motor which released the brake, reversing the polarity driving the brake on. (At this stage I don't think I need to do this as it comes on & off on the XJ as stated)
Any information around this problem is appreciated thank you all for your input, this is the first problem I have had with the XJ so just trying to find my way around the car.
Cheers

[iRS]

I managed to find the diagram from that old post.

Agree on motor conductors being Ok. I guess that leaves the hall effect switch conductors to check.

[goldy1]

That's great thanks for the diagram should help to track the problem down.
Thanks for your time and trouble

[goldy1]

Whilst trying to trace fault I found this info bulletin XJ206-07

On the EPB actuator side of connector CV7(under the vehicle) check resistance
between the following points:
• Pin CV7-1 and ground (pass value: open circuit = resistance above 10 megaohm).
• Pin CV7-6 and ground (pass value: open circuit = resistance above 10 megaohm).
Can anyone tell me the position this CV7 connection is description saying it's under the vehicle?
Not having access to a lift some idea of where to look would be a big help as some wires from the brake switch and the module have a LOW READING TO EARTH

[iRS]

I'm pretty sure its the one connecting the motor to the sub frame harness. Its not easy to get at. Its high in the subframe towards the back on the passenger side.

[iRS]

I think this is what you are looking for.

Note: this is not my car. I think the diff has been removed here.

[goldy1]

Thank you much appreciated, that's got to be a big help in locating the connection.

[goldy1]

Having checked all cables it turned out to be the worst possible cause, the hall effect sensor which looks like a very big job to replace. why did they ever stop fitting a simple lever?

[iRS]

That's unfortunate. I guess that means removing the EPB. Its a job not to be recommended. You can review my account of doing that here: viewtopic.php?f=285&t=14027

Unless you can get the car up at height you might want, at this point, to think about taking it to a decent Indie. I think if I were to do the job again, I would probably remove the diff. I think it might all be a lot easier with the better access that would provide.

Good luck.