mitch236

Ok, last weekend my car went into complete brake failure mode. Orbit Racing had their PIWIS on hand and this is what we found:

PAS #8053 Electric steering column lock continuously blocked

POSIS #C152 Communication failure PSM control unit

RDK #8003 System disturbance

Front #8021 Luggage compartment light (I unplugged it)

REAR #C128 Communication with PAS (comfort) control unit
#C123 Communication with passenger (comfort) door
#C122 Communication with driver door


After he cleared all the fault codes, the brakes worked.

My car is stock except:
Driver and passenger seat change which was followed with reprogramming. Removal of the trunk light (which I replaced to clear the fault) and all front trunk carpeting and installation of a cool suit cooler.


Hopefully someone can help me figure out what all this means.

eclou

It means it's time to get a dedicated track car. Complete brake failure is not something I would ever want to pop up again. Are you still running oddball sized tires?

mitch236

Yup, still using the "oddball" sized tires. Notice the lack of any ABS faults?

eclou

have you thought about running 1 session with the stock tire sizes to see if the phenomenon recurs?

mooty

how oddball are your tire size?
this sounds scary.
i did the seat mods and airbag, seat belt warning lights as well. i did the same on cayman (which i presume has similar computer brain for this purpose) so far i dont have brk prob. and i logged 5k track miles on the cay.

i hope it's the tires that's causing the prob, which would be the easiest to fix vs. re-working the computers.

mitch236

Sorry if you missed the other threads but two other GT-3's in my club are having the same brake issues and both were running stock wheels/tires. Now only one of the GT-3's are running stock tires. It isn't a tire size issue. It is driving us all crazy. The codes don't really make sense and the worst thing would be if it was just a coincidence that the car corrected after clearing the codes.

BTW, the tire sizes aren't really oddball.
They are 235x40x18 on 9" and 315x30x18 on 12"

doc2s

try to find a good dealer to help you with this. although most dealers are clueless, they will get porsche involved.

insite

wow, that's a lot of faults. what's the common denomenator? me thinks it's a ground fault. with your alarm system. the alarm module under the driver's seat monitors the steering lock, both doors, the luggage compartments, etc.

unhook the battery and remove the driver seat. check to see if the unit's ground wire has a clear path to the chassis. there's a possibility that not enough paint was removed from the floor board to give a good connection.

go to the track and what do you get? heat. this increases the resistance in the connection and gives ground fault issues. this is just an educated guess.

Mike K.

Sounds like a very well edumacated guess to me!

NoSubEDU

I take it it's not a steel vs PCCB issue??

930man

nosub ...did you get a 997 gt3 yet?

mitch236

All three cars that I know of have steel. The more we investigate this issue the more we are thinking the fault codes aren't associated with the problem. The race shop that is looking into this has alot of connections in Germany and the word is that it may be a valve that is in the power assist vacume line. Since I'm not a mechanic, I can't give an opinion but it sounds plausable. Apparently there is a one way valve that will hold the vacume in the power assist in case of engine failure for at least a couple of pumps. I was told that this valve has been known to stick and stop vacume from reaching the unit. I was told that an easy fix is to "remove" the valve and let it be an open line. It seems to make sense.

Any thoughts?

Hank Cohn

Mitch,

Is there any further description available on the following two error codes? I googled it but found nothing.

POSIS #C152 Communication failure PSM control unit
RDK #8003 System disturbance

It would be very interesting know what would trigger both of those faults and even more interesting to read a description of the resultant set of lost or diminished functionality.

It does look like you are right and this has nothing to do with tire sizes and ABS. I would have sworn that the issue as I have experienced it in 2 track prepared 993s and my '99 Cup when experimenting with different tire selections. Cars have become very complicated and it will be interesting to learn the true problem and solution.

I wonder if this anomaly is specific to your track and a certain turn/track surface that doesn't exist anywhere else. Have you or others experienced this on other tracks or on the street? I thought the PIWIS (SP) system communicated back to the factory. Is that only true at the dealership? One would think that Porsche would be very interested in your problem. Have you called any of the premier Porsche shops like Farnbacher Loles?

Thanks for sharing,
Hank

Hank Cohn

Mitch,

Is there any update? I am very interested in your findings.

Thanks,
Hank

mitch236

So far, the only thing I know is that the faults do not explain the problem. The shop with the PIWIS has an account with Porsche and they called Germany and were told that while they need to figure out what all the codes mean, they wouldn't affect the braking. So now, I am of the belief that the tire sizes are the issue. The only problem is that in order to run MPSC's, I would need to run 345/30's in the rear and I don't think I can make them fit. The other option would be to change the ABS sensor in the rear to accept the 315's. I think that may be possible. We are looking into it.