Thread: Park Brake Fault C1A48-01

I have the dreaded park brake fault on my 2012 Discovery 4. The park brake works as normal it engages and disengages with the switch and disengages with application of the accelerator. The fault light will go away after a few starts if the park brake is not used.

The fault manifested itself the day after a day trip sand driving in Fraser Island, back in January, I thought it may be salt water or sand contamination into one of the plugs or into the park brake module itself.
I had the scan tool put on during my service last week, the garage told me the DTC code was C1A48-01, unfortunately I could not afford to pay them to look into it as I am facing a stand down at work due Covid 19. I will have plenty of time to have a look at it myself and do not necessarily need to use the car.

So far I have checked continuity on the CAN bus wires between the park brake module and the plug C0376 on the rear left hand of the chassis rail, these were good. I realise I will have to go further to look for shorts and voltage drop in the circuit. The plugs were dry and seemed well protected with no contamination.

Does anybody have any previous experience with this fault, tips about where to look and what its fix was? Any help appreciated, thanks.
There are no other faults.

After much head scratching and trawling through forums I finally came up with a fix for my Park Brake Fault and associated DTC C1A48-01.

It was a broken wire between connector C0376 and the BCM, the LR manual is misleading about this.

For those of you that want more detail and as to how it took so long to find, read on and refer to the wiring manual pages if you can:

For DTC C1A48-01 the D4 workshop manual suggests the below troubleshooting actions which in my opinion are misleading:

Check the parking brake actuator module to instrument
cluster warning lamp circuit. Refer to the electrical circuit
diagrams. Rectify as necessary. Refer to the warranty
policy and procedures manual if a module is suspect. Clear
DTCs, complete drive cycle 1 to test for normal operation

Referring to the D4 wiring diagrams 265-05 and 418-00 the only circuit that goes from the park brake actuator to the instrument cluster is the high speed CANBUS. I checked for continuity and shorts on high speed CANBUS at various points on the car and everything checked out OK. I also checked all of the wires in the short run from the EPB to the connector C0376 on the chassis rail, again no faults.

If the wiring is good Land Rover suggests that the park brake module or the instrument cluster may be faulty $$$$$!!. I almost pulled the trigger on spending $2K to have the EPB module replaced. I discussed the issue with a mechanic at my local LR specialist who said that this fault looks like a wiring problem, and I should look further into it before changing the EPB. So subsequently I checked the splices in the CANBUS loom in the LH rear of the vehicle and almost considered cutting the CANBUS at the EPB to see if it created any other faults, as the EPB is the last module on the CANBUS. Again I could not find any faults.

So it was back to the trawling the internet, researching the Kuester (EPB vendor) website and BMW wiring diagrams. BMW use what looks like to be exactly the same park brake actuator, I found nothing of value here. During this time I chanced upon a D3 EPB wiring diagram.

The D3 EPB wiring diagram 206, shows that in addition to the HS CANBUS there is a “signal lamp” circuit that goes directly from the EPB to the instrument cluster.
Cross referring this diagram to the D4 diagram this signal lamp (now called status lamp) wire goes from the EPB to the BCM, on the D4 the status lamp (P) is then triggered from the BCM over MS CANBUS to the instrument cluster.

My presumption for the D4:

Is that this signal lamp circuit gives a discrete signal to the BCM that illuminates or extinguishes the RED park brake applied symbol via MS CANBUS to the instrument cluster. In the D4 if this disagrees with the HS CANBUS signals it brings up PARK BRAKE FAULT message and DTC C1A48-01. This is only my presumption based on what I know about aircraft systems and I have no technical data to back this up.

Back under the car to check this circuit from connector C0376 (L/H rear wheel arch on top of the chassis) forward towards the CJB.

Adjacent to the back of the connector there was a discoloration to the GREEN wire in question, I probed the wire pushing a pin through the insulation (not recommended unless you plan to seal it back up again) and voila there was no continuity from the pin in the plug to where I pushed in the pin about an inch back from the connector.

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To repair the connector, I pulled out the grommet behind the wheel arch out and pulled the connector and loom into the rear load bay after removing the LH rear sidewall. I removed the pin from the connector and soldered on a new piece of wire, I cut back the old wire and spliced the new piece into the loom with a solder splice.

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If you download the connector diagram from Topix it states on diagram that the “connector housing is not serviceable”. This is absolute rubbish, information on how to dismantle and repair the connector is available from the manufacturer TE along with part numbers of pins and sockets. https://www.te.com/usa-en/product-1438842-1.html. Plug and socket can be pried apart and pins removed with basic tools, pliers and small screwdrivers.

I believe that some of the D4 workshop manual text has not been amended to reflect the change from Discovery 3 systems to Discovery 4 and the troubleshooting for C1A48-01 still refers to Discovery 3 wiring. The D4 vehicle workshop manual troubleshooting instructions should be amended to read:

Check the parking brake actuator module to body control module
status lamp circuit. Refer to the electrical circuit
diagrams. Rectify as necessary. Refer to the warranty
policy and procedures manual if a module is suspect. Clear
DTCs, complete drive cycle 1 to test for normal operation

The information from TE.com about dismantling the connector was invaluable, scroll down to the instruction sheets on the webpage. The repair parts cost me $7.

THanks for reading, I hope this helps somebody else.

Michael.