Parking Brake Fault got me G-Force and Gear Shift (also, $4500 in parts...)
08-03-2016, 10:07 PM
#1
Drifting
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Parking Brake Fault got me G-Force and Gear Shift (also, $4500 in parts...)
A couple months ago I had a random parking brake fault warning appear on the MID when I started the car after having parked it with the parking brake engaged. The parking brake still appeared to be holding the car when engaged and releasing when disengaged, and the next time I started my car even after having engaged the brake, it didn't reappear, so I dismissed it as gremlins. Then it happened one more time a few weeks later and again went away, so I dismissed it again, but then it started happening about 85% of the time I started the car. So after 3 days under that condition, I brought it to the dealer. Turns out that even though it appeared to be behaving correctly, quite a bit had gone wrong, as described in the summary below. The car ended up in the shop for 10 days over this due to 3 rounds of ordering parts triggered by 2 failed calibration attempts over the course of several calls with the Porsche mothership in Germany. I got to see the work order on my SA's computer that actually listed cost information (my paperwork just says "WARRANTY" for all cost items) and the parts alone came to $4500. Labor showed as $1500, but my SA said they hadn't even finished recording all of that yet. I told him that if my car hadn't been under warranty, I would've been none too pleased to get a $6000+ bill for a parking brake that doesn't seem an improvement in any meaningful way over the traditional version that uses a $20 cable and no sensors or motors.... Although I guess it could've been worse. Considering the rotors ended up being replaced, I could've been out of warranty and had PCCB. 
(In fairness, from what I've read about Porsche, I would bet they'd have goodwilled a solid chunk of this out of warranty because of the sheer absurdity of handing a customer a $6000+ parking brake repair bill.)
The dealer told me that even though they didn't think I had done this, the parking brake condition when they got it resembled what they would expect to see on a car that had been drifted via parking brake, which I don't even see as possible with an electronic brake, at least not with any degree of precision. I have no idea what went wrong here. I use my parking brake everywhere I park, even on level surfaces, except when I'm at the track, and nothing ever seemed amiss. However, now that I have the car back, the parking brake engages noticeably faster (~1.5s rather than 2s) and the release sound is noticeably different from the engagement sound, whereas before they sounded identical. Maybe that will change with some use, but I don't remember the parking brake speed or sound changing since picking the car up new.
Anyhow, on the plus side, part of their troubleshooting involved updating my car's software. That reset all of my MID settings (and disabled the one-touch function on the driver's window, but that's easily retrained), but while re-disabling most of the MID panes that I never use anyway, I saw G-Force and Gear Shift Assist in that list, and both of them work. I did not ask for them to try to enable this, so maybe there isn't a trick to this after all other than just installing the latest software as the paperwork notes?
Lastly, does anybody know what the "spreaders" mentioned in the write-up below are that prompted them to replace my rear rotors? Or are the "drums" part of the rotor assembly? I see them mentioned as having been damaged but don't see them called out as being replaced. And does anyone know what/who DSM is?
(In fairness, from what I've read about Porsche, I would bet they'd have goodwilled a solid chunk of this out of warranty because of the sheer absurdity of handing a customer a $6000+ parking brake repair bill.)The dealer told me that even though they didn't think I had done this, the parking brake condition when they got it resembled what they would expect to see on a car that had been drifted via parking brake, which I don't even see as possible with an electronic brake, at least not with any degree of precision. I have no idea what went wrong here. I use my parking brake everywhere I park, even on level surfaces, except when I'm at the track, and nothing ever seemed amiss. However, now that I have the car back, the parking brake engages noticeably faster (~1.5s rather than 2s) and the release sound is noticeably different from the engagement sound, whereas before they sounded identical. Maybe that will change with some use, but I don't remember the parking brake speed or sound changing since picking the car up new.
Anyhow, on the plus side, part of their troubleshooting involved updating my car's software. That reset all of my MID settings (and disabled the one-touch function on the driver's window, but that's easily retrained), but while re-disabling most of the MID panes that I never use anyway, I saw G-Force and Gear Shift Assist in that list, and both of them work. I did not ask for them to try to enable this, so maybe there isn't a trick to this after all other than just installing the latest software as the paperwork notes?
Lastly, does anybody know what the "spreaders" mentioned in the write-up below are that prompted them to replace my rear rotors? Or are the "drums" part of the rotor assembly? I see them mentioned as having been damaged but don't see them called out as being replaced. And does anyone know what/who DSM is?
Last edited by jphughan; 08-03-2016 at 10:30 PM.
08-03-2016, 10:19 PM
#2
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See the left end of item 6 below.
08-03-2016, 10:20 PM
#3
Drifting
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The spreaders are probably the components that extend out of the parking brake motor assy when it's being applied. Being jammed would imply they weren't retracting when the motor attempted to retract them. On a hydraulic drum brake these are the same parts that extend out of the hydraulic slave cylinder when the brakes are applied.
08-03-2016, 10:21 PM
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I assume the spring mechanisms that spread apart the drum brake pads for the e-brake.
To wit, the parking e-brake does not use disc hardware... it uses a drum around the brake rotor disk for the parking brake. So there is separate hardware for this. At least, in previous models... so I assume it is the same.
Yes, your modern Porsche has both disc and drum brakes.
If I had to guess, the ultimate culprit was heat... caused by the e-brake not fully disengaging on the rotor drum. This would fry many components in that area, and it looks commensurate with those very parts being replaced on the work order. What caused it to not fully disengage? Likely a physical malfunction of the drum brake pas spreader mechanism, not allowing a full release.
So, here's a theory... it would be possible for the emergency function of this brake to be engaged at speed, say on a track, by pushing with your knee. Now, many lights would come on with the dash, and then you would have to manually release it after engaged, so I am sure you would have realized if it happened.
But due to location of the switch, and being activated by pushing... I could see it happening eventually. But likely not what happened in your case.
To wit, the parking e-brake does not use disc hardware... it uses a drum around the brake rotor disk for the parking brake. So there is separate hardware for this. At least, in previous models... so I assume it is the same.
Yes, your modern Porsche has both disc and drum brakes.
If I had to guess, the ultimate culprit was heat... caused by the e-brake not fully disengaging on the rotor drum. This would fry many components in that area, and it looks commensurate with those very parts being replaced on the work order. What caused it to not fully disengage? Likely a physical malfunction of the drum brake pas spreader mechanism, not allowing a full release.
So, here's a theory... it would be possible for the emergency function of this brake to be engaged at speed, say on a track, by pushing with your knee. Now, many lights would come on with the dash, and then you would have to manually release it after engaged, so I am sure you would have realized if it happened.
But due to location of the switch, and being activated by pushing... I could see it happening eventually. But likely not what happened in your case.
08-03-2016, 10:25 PM
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They act like a miniature drum brake that operates inside the "hat" of the disc rotor assembly. So the hats were damaged, not the rotors, but since they aren't a 2 piece design, the entire rotor must be replaced.
08-03-2016, 10:27 PM
#7
Drifting
Thread Starter
I assume the spring mechanisms that spread apart the drum brake pads for the e-brake.
To wit, the parking e-brake does not use disc hardware... it uses a drum around the brake rotor disk for the parking brake. So there is separate hardware for this. At least, in previous models... so I assume it is the same.
Yes, your modern Porsche has both disc and drum brakes.
If I had to guess, the ultimate culprit was heat... caused by the e-brake not fully disengaging on the rotor drum. This would fry many components in that area, and it looks commensurate with those very parts being replaced on the work order. What caused it to not fully disengage? Likely a physical malfunction of the drum brake pas spreader mechanism, not allowing a full release.
So, here's a theory... it would be possible for the emergency function of this brake to be engaged at speed, say on a track, by pushing with your knee. Now, many lights would come on with the dash, and then you would have to manually release it after engaged, so I am sure you would have realized if it happened.
But due to location of the switch, and being activated by pushing... I could see it happening eventually. But likely not what happened in your case.
To wit, the parking e-brake does not use disc hardware... it uses a drum around the brake rotor disk for the parking brake. So there is separate hardware for this. At least, in previous models... so I assume it is the same.
Yes, your modern Porsche has both disc and drum brakes.
If I had to guess, the ultimate culprit was heat... caused by the e-brake not fully disengaging on the rotor drum. This would fry many components in that area, and it looks commensurate with those very parts being replaced on the work order. What caused it to not fully disengage? Likely a physical malfunction of the drum brake pas spreader mechanism, not allowing a full release.
So, here's a theory... it would be possible for the emergency function of this brake to be engaged at speed, say on a track, by pushing with your knee. Now, many lights would come on with the dash, and then you would have to manually release it after engaged, so I am sure you would have realized if it happened.
But due to location of the switch, and being activated by pushing... I could see it happening eventually. But likely not what happened in your case.
But if the e-brake wasn't fully disengaging before, maybe my car will be much faster now!
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08-03-2016, 10:48 PM
#8
Trust me, you would know. If it's anything like a Bmw, that will bring the car to an forced emergency stop.
08-04-2016, 03:24 AM
#9
Rennlist Member
What was so bad about a handle and cable???
Not a fan of electronic e brakes.
Not a fan of electronic e brakes.
08-04-2016, 03:53 AM
#10
Drifting
Thread Starter
That's what I've been asking myself! The only benefits I've been able to come up with are automatic disengagement when you drive off (but even the old version could flash lights and make noises about this), reduced footprint in the cabin, and I guess from the manufacturer's perspective an inability for customers to reasonably drift with the e-brake. But those just don't seem like significant benefits even at an identical cost to the legacy setup, never mind given the cost of 2 motors and a control unit!
08-04-2016, 07:54 AM
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That's what I've been asking myself! The only benefits I've been able to come up with are automatic disengagement when you drive off (but even the old version could flash lights and make noises about this), reduced footprint in the cabin, and I guess from the manufacturer's perspective an inability for customers to reasonably drift with the e-brake. But those just don't seem like significant benefits even at an identical cost to the legacy setup, never mind given the cost of 2 motors and a control unit!
I agree, electric parking brakes are a downgrade from a cable operated hand brake.
08-04-2016, 10:45 AM
#12
I have the same problem on my car....dealer has no clue on how to fix. Maybe you work document will give them a clue on where to start and what not to do.
08-04-2016, 10:59 AM
#13
Drifting
Thread Starter
Well like I said, the document involved creating a PTEC (call to Porsche HQ) and then contacting DSM, whatever/whoever that is. First they replaced just the damaged hardware and the motor on the affected side, but it wouldn't calibrate at that point, so they worked on some other stuff and Porsche eventually told them to replace the second motor, which still didn't allow it to calibrate and finally they said to replace the control unit as well. At that point they'd replaced every part in this whole assembly.
08-04-2016, 09:16 PM
#15
Well like I said, the document involved creating a PTEC (call to Porsche HQ) and then contacting DSM, whatever/whoever that is. First they replaced just the damaged hardware and the motor on the affected side, but it wouldn't calibrate at that point, so they worked on some other stuff and Porsche eventually told them to replace the second motor, which still didn't allow it to calibrate and finally they said to replace the control unit as well. At that point they'd replaced every part in this whole assembly.
I sent a copy of your warranty paperwork and have to take my car Monday....they plan to go straight to the module that controls the brake. Another user here in RL had a similar problem and it was the module. Of course they will also check the mechanical parts to make sure they are not damaged. Crossing my finger it will get solve and thank for posting the info.
