I recently purchased a 2008 LR3 with the knowledge that the parking brake module was malfunctioning, and since it was a decent price for my area with relatively low miles for the year, I decided that, worst-case scenario, I could just replace the EPB module and still feel good about my purchase. However, before I purchased the new unit I wanted to do some investigation into some of the other possible reasons this could be happening, to avoid things like replacing a unit that isn't faulty, or immediately destroying a brand new unit because another issue, like wiring.

So, this afternoon, I used my Gap IID tool to read the fault codes. The code that kept showing up was: "C1A00-4B control module system internal failure - over temperature error"

Then I removed the cover of the EPB while it was still on the vehicle to get a good look at what was going on. What I found was that the lead screw mechanism was NOT jammed like so many other instances I've read about. I could both turn the splined rod easily with a screwdriver AND I could use the IID tool to execute the "unjam" command. I issued the unjam command and watched the lead screw back off, and quickly stop when it realized it was moving without any load, several times.

My conclusion, so far, is that the usual issue of a jammed mechanism or stripped gears is not the case in my situation, because the motor will turn when it ignores the non-nominal temperature sensor feedback.

Could this just be a failed internal temperature sensor? Of the two dozen or more threads I've read and videos I've watched about this issue, not one has mentioned a temperature sensor failure with no jamming of the mechanism whatsoever. Anyone have any ideas?

Here is a screenshot of the realtime data from the Gap IID tool relevant to the EPB module, and some pics of the inside of the module:



The realtime data says Control Module Internal Temperature: N/A. Should it be showing a temperature?

 

The ridiculously out-of-range motor current reading is also a little perplexing, but it did read a more reasonable 0.5 A from time to time while I was watching it.

 

Apparently, if I clear the fault I can get some movement out of the motor for a second or so, by pulling up on the parking brake switch, before the over temperature fault triggers again. When I use the parking brake switch, the over temperature fault triggers and stays on, when I use the unjam command in the GAP tool the motor moves and the fault triggers momentarily and turns off, and when I use the "latching" or "mounting" command in the GAP tool there is no movement in the motor at all, and the fault triggers and stays on.

Clearing the fault with the GAP iid tool removes the amber "BRAKE" light, but the flashing red "PARK" light never turns off.

I also tried holding the parking brake switch in the up position for 5 or so seconds, then doing the same in the down position. No idea what that would accomplish, but I saw somebody say it worked in the disco3 forum. It did nothing for me but trigger the fault.

 

Sounds like a faulty circuit board. I would suspect a cold soldier joint, that is a solder joint that has cracked and creates na open circuit or an intermittent one. But one would need to examine that board closely to find out. Locating the temperature sensor itself would help, but I am guessing its integral in some way and not obvious. So maybe you might have luck buying a used module and swapping just the PCB board if that is even possible. Or you have to remove it, examine it. Locate the temp sensor to test, etc. In short, it really seems defective and replacement or repair are you only options. I dont think you can test any further.

 

Thanks for the reply, DakotaTravler. That's about the same conclusion I had come to.

I'm ready to replace it with a new unit, but I want to do it myself to avoid the the labor cost. I've read here and there that the replacement module must be new because it's VIN-locked or something like that (which seems strange to me), and that it needs to be calibrated, or flashed before using it. Does anyone know the process of calibrating or flashing the EPB module after installation? In the GAP tool menu, there are options both for longitudinal sensor calibration and also the option to flash/update the module itself, although, when it pull up that menu now, it say "Equipment Not Available". I know all about the adjustment of the shoes, as I have done that twice now, in an attempt to work out what exactly was wrong with the EPB in the first place.

 

Shoot GAP an email, they are very helpful. I have not heard they are vin-locked, could be. But the GAP tool may be able to take care of that.

 

When you operate the EPB does it apply the parking brakes

 

Have you looked on the UK site? There are myriad posts on the EPB, admittedly most about repairing, delatching, etc. I've read posts in the past about replacing the module having had EPB problems in the past. Worst case ask Disco Mickey if he'd be able to talk you through it if you can't find anything.

 

Globetrotter, no it does not apply the parking brakes. I took a few short videos of the operation while I had the cover off and it seems to actuate the lead screw 5-10 mm, then immediately backs off by 10-20 mm, presumably because the module throws the code almost immediately. I've entertained the thought that maybe there is sticking in the cables, or the brake shoes themselves, but that wouldn't explain why the flashing red "PARK" light never turns off. It seems like the module PCB is cooked, like DakotaTravler said above.

Pagoda, I have looked at the UK Disco3 and even bookmarked a few threads about the EPB, but I admit I haven't taken as deep a dive there as I have here and just in general google searches. I'll check it out, and see if I find anything relevant.

At the moment, I have a couple of other more pressing issues to deal with on the LR3, so I might leave the EPB alone for a little while. I was hearing a hollow scraping noise (bad bearing sound) when I coast around 15-35 mph so I jacked up all four wheels and let them turn. It sounds like it's coming from the driveshaft center bearing. I'm crossing my fingers that's what it actually is and not my rear differential. I'm also now seeing just a drop of oil at a time at the outer end of the passenger side outer tie rod steering boot, so it seems like my rack and pinion is leaking. Yay.

 

Back at the EPB, if it does not operate the brakes then the cables may be seized at where they go into the back plates. Remove the wheels and drums and have a look.