981 "PSM Failure" and "Stop/Start Inoperative" warning

[BrianJ]

Widely reported elsewhere (eg 991 Forum) but can't see here. Cause seems so unlikely thought worth reporting.
Had "PSM Failure" and "Stop/Start Inoperative" warnings after driving for an hour or so at steady speed on motorway. Message says you can carry on driving carefully. Brakes seemed to be dragging slightly when slowing to stop. Messages disappeared overnight (I was on hols), but reappeared again after another couple of hours.

Quickly diagnosed and sorted by Porsche Centre Wilmslow (first time I have used them). The cause seems unlikely, but is plastic bushes at the ends of the brake pedal pivot pin which swell slightly when warmed by the heater, causing the pedal to not release properly. Can also lead to brakes dragging and overheating.
Fix is replace the pivot pin and both bushes. Took them about an hour and a quarter, including safety check which spotted a tiny screw in a rear tyre (about 2mm dia!). Good service from them.

 

[notechmike]

I had same thing a few weeks ago. I first noticed that brake lights stayed on for a fraction after I released the pedal. Then the delay got bigger and bigger. Then I notice the car pulling up quicker than I expected when free wheeling to junctions. I went to Dealership and they said its just one of those things about PDK learning your driving style?? Anyway I think you can guess what I thought about that suggestion so I posted on Boxa.net and was told about the bush issue. Rang same dealership next day and told them it wasn't anything to do with PDK learning my driving style but this problem with pedal bush making brakes stay on longer than they should. The immediately told me to stop driving the car and arranged for a trailer recovery to dealership plus a hire car. Got my car back a day or so later all nicely cleaned and checked. Problem fixed. No charge of course. You would have though if it was this big an issue they would have done a recall on effected models - apparently it was a batch of bushes used on early versions of the 981 - mine is coming up to 2 years old. My only residual concern is how much did this prematurely wear my discs and pads?? I don't suppose I will get an allowance when it comes to replacing them. PS If you want to check your car just open roof put heater on full blast into footwell and within a few minutes you should notice brake lights staying on when you release pedal - well you will notice it if you have the problem and its dark outside ;-)

 

[chrisH]

It has also been reported on the Cayman section by myself. You were lucky if they fixed it while you wait as mine was a two week wait and half a days labour to fit as clutch pedal has to come out to access brake pedal bushes. As all the current generation cars use the same parts it is obviously a common problem. What amazes me is why it has not been the subject of a recall hence it is a surprise to owners when it eventually happens. Heaven help you if this happens when you are miles from a dealership.

 

[BrianJ]

An unexpected advantage of PDK! When I learned the cause I did wonder whether a squirt of WD40 would have provided a temporary fix if I hadn't been passing a Porsche Centre. In serious cases within warranty I guess it is Porsche Assist and a trailer.

 

[H14PDB]

It happened on my Cayman when I was away with work and wife had to deal with it. Took two attempts to fix, yet seems a common fault. Why no recall for something like this?

 

[chrisH]

Yes, I did raise this with my OPC at the time and they confirmed no recall issued, even though a lot of 991's had suffered the problem. What also baffles me is that my car had covered several thousand miles when it occurred so I am not convinced it is due to the footwell getting hot and the bush expanding since the bush and pedal shaft are made of plastic not metal.

 

[BrianJ]

My Boxster didn't show the problem until >10k miles. But the two occasions on which it occurred were both after driving for more than an hour, the car having been cold at the outset on both occasions. So my experience matched exactly the explanation given by the Porsche Centre, however unlikely it sounds. And why it takes >10k miles to develop interference between the shaft and the bush is another mystery.

 

[chrisH]

ORIGINAL: BrianJ My Boxster didn't show the problem until >10k miles. But the two occasions on which it occurred were both after driving for more than an hour, the car having been cold at the outset on both occasions. So my experience matched exactly the explanation given by the Porsche Centre, however unlikely it sounds. And why it takes >10k miles to develop interference between the shaft and the bush is another mystery.

Agreed, I had driven my car to Germany and back with typical 5 hr stints daily so I don't buy this "caused by hot footwells" explanation. One would have thought that grabbing brakes were a safety issue worthy of a recall but my OPC said that Porsche do not agree, whereas the service indicator software update was a recall item.

 

[Motorhead]

Chris, You do have to wonder how long before a safety-related issue like this becomes a full recall. Maybe someone has to have a serious accident with life-threatening injuries before the company reacts to it. Look what's happened to Honda over the non-reporting of airbag issues - a huge fine and the CEO replaced. Jeff

 

[chrisH]

Jeff, When this fault occurs it is difficult to pull away without stalling as the brake grabbing can be severe, this happened to me at a set of traffic lights and I was wondering if someone was going to rear end my car before I managed to get going before they went red again. The OPC techie who changed mine said they had a 991 that could not even be trailered as the brakes were locked full on, it had to be lifted on. If that is not a dangerous situation, then what is? Chris

 

[andyhalligan]

Thanks to reading this thread, I now understand why my stop/start function and clutch disengagement on PDK didn't seem to be working. As soon as I told the dealer [OPC Bolton], they immediately admitted that it was the 'bushes' problem and have booked me in for a replacement. I only noticed slight symptoms when driving, in that the car felt a little sluggish, but would never of thought I had a real issue other than the car wasn't doing the eco things as it used to do. An early sign of this was a few weeks ago when I set off down the road and a message came up telling me reverse could not be used, so I stopped the car, switched off and on, and it went away. So, as this article was so useful to me to read, I thought it would serve others to share my experience. You would think they would carry out this work routinely when the car goes in for anything else!

 

[BrianJ]

Excellent, that's why I started the thread, even though similar things have appeared elsewhere. Thanks for taking the time to make your positive feedback.

 

[Chris_James]

I had the same failure at just over 3K miles. Car was almost undriveable with brakes seized on, trailered back to Porsche and fixed with new bushes in 2 days. I didn't realise what a common problem this is. I asked them to check discs and also had a look myself, but I only went a short distance and they were nowhere near as hot as they would get on a track day or hard driving. The warning message indicated a problem with stability management but said the car was safe to drive!!

 

[Jarmin]

My Cayman has suffered this fault today trailer back to OPC in the morning not happy that this is not an official recall by porsche uk it is a known fault. I intend to complain it felt awful when it happened fortunately i was not travelling at speed ridiculous issue from Porsche disappointed, and I agree with the comment above re over heating my heat setting was less than half rant over until Porsche contact me.