Alan

I think it is probably normal behaviour for the controller to shutdown. It has a range of expectactation of normal conditions - rear wheels both spinning faster than the front and likely at different relative speeds for an extended time probably convinces it that its sensors must be toasted... These conditions certainly aren't getting you max performance.

There are error conditions you can read out of the diagnostic port with a hammer to find out what happened.

Not sure if it actually applies to the PSD but there are error codes for other control units that Porsche describres as "Sensor Values Implausible"... in this instance it figures it may be doing more harm than good and shuts itself down for safety... very logical.

So in the meantime maybe you should switch tire brands or buy some new ones...

Alan

9x8

That's pretty good idea, I have those Gemballa 18" rims laying in my garage, so I guess it's time to get some tires for those.

worf928

I'm pretty sure that is normal. If the ABS/PSD has come to a decision that some part of the system is faulty the safest thing to do is to discontinue operation. There are several warning conditions that are persistent until the ECU in question is power cycled.

Have you connected a Hammer and interrogated the ABS/PSD ECU for error codes?

Cheburator

Quick update,

I figured out the original problem - it was a leaking slave cylinder - after a weekend at the Ring I noticed that I was loosing brake fluid from the PSD reservoir. Unfortunately by the time I figured it out, my lovely G28.55 was toast - the pinion/crown wheel had teeth missing.

Running a G28.57 now with a brand new slave cylinder attached

Vilhuer

Did fluid leak inside gearbox? There is rubber booth between slave and fork which job is to prevent fluid from geting in. Just one more thing to check reqularly.

9x8

Didn't have the opportunity yet, and probably won't in near future. :|
I'll get my hands on one eventually tho, so I will check if the problem is still there.

SteveG

Details on how you check this?

Vilhuer

Either take out rear diff cover or remove PSD slave cylinder and check there are no holes rubber booth. Removing slave is better idea as its possible to check it is leaf free at same time.

TheoJ

on a GTS just keep an eye on the fluid level in the reservoir. If it drops without reason it is time to investigate.
Did you guys know that there is a small window in the rear wheel liner that you can open for this purpose? I think this starts with the GTS model. Just lift the driver side rear to get some extra wheel clearance, two little screws and open the window. Use a flashlight to peek in. Takes no more than 5 mins.

regards
Theo

worf928

The Hammer would, theoretically, indicate which sensor - among other things - might be bad.

bhauser928

Hello everyone. First time post here. I have a '94 928GTS with an automatic transmission. Owned it for 11 years now. Last winter, I was entering the interstate on a very cold day and drove over a very rough spot on the entrance ramp while accelerating (about 45MPH). The crappy pavement really rocked the car and immediately on the digital display appeared the message "clutch control off" with the clutch control symbol in the message box. I checked my original owners manual and it simply states that if this error message is encountered, to take the car to the dealer for $ervice.... My question(s) to anyone here is... What is this error message? Is there any way to address the problem causing it? Should it be fixed sooner rather than later...or even at all? It doesn't seem to affect the performance of the car and the traction control still operates properly....as there is still much sand on the streets around here. The warning seems somewhat intermittent, as it was on for some time after this incident, then, after winter storage, was off until last week...June, 2011. Any information would be greatly appreciated. Thanks, Brian.

Herman K

If you drive most off the time on smooth roads the PSD may not get activated for long periods of time and the slave (pin) in the transmission can get stuck or the electric motor that drives the pump.

Regular maintenance requires flushing of the fluid and exercising the slave pin the “hammer” Porsche tool nick name for KTS300 can take care of these requirements (if you us search you may find some other work around methods).

When I first did the required maintenance on my car it took quite a while for the slave pin to brake loose now it gets exercised at least 2-3 /yr and it’s happy.

I just acquired a complete spare PSD and going through it I found that he electric motor that drives the pump had seized as it had been sitting around for some time by taking it apart I managed to lube it, got the shaft to spin freely and now she is working fine.

Good luck

LarryM

So, I gather that if I have issues with wheel spin above 20mph I need to invest in better tires/grip?

I'll flush again, its been 6 years on the current fluid.

LM