Banango

I searched but didn't find reference to this problem, which I hope is now solved. My SA said my dealership had seen it once before, in a 2014 GT3. Ours is a 2015 GT3 (F engine).


Problem:

Occasionally, and with increasing frequency, pulling away from a stop in 1st gear the car would bog. Regardless the throttle applied, up to about 90% and a couple of times even at WOT, it would move slowly but steadily until an up-shift to 2nd gear.

After the up-shift power would usually come on very suddenly, but occasionally the slowness would continue for a while and then there'd be a sudden shove and attendant exhaust note even at fairly light throttle. The behaviour generally manifested with a warm engine. It was never experienced in a gear above 2nd.

The behaviour could be slightly worse on uphill starts. It was intermittent and largely random but increased in frequency between March and June. Once it began on any given outing, it generally (85%) continued until the car was turned off. While the slow acceleration or bogging was taking place the car sounded normal for its various engine speeds.

The feeling was somewhat like a throttle position sensor failure. Sometimes it felt like a clutch slipping. I have experienced some limp modes in BMWs that felt similar.

The symptoms didn't manifest on track, only street. It made for some fairly scary crossings of main roads and merging at uncontrolled junctions.

The car has cruise control. As the frequency of the problem increased, the CC became increasingly unreliable. If it activated, it would work fine, but increasingly it could not be activated at all.

There were no dash lights, warning lights, etc. There were no visual indications of a problem.


Solution:

This was diagnosed as a bad brake switch. The OBD fault code it eventually displayed was P0571. In the 2014 car that had the same problem previously, the switch was separate from the master cylinder. At some point in the build cycle it was apparently integrated so a new master cylinder was installed in our car and the brake system was flushed. Our PDK software was also updated.

The cruise control was apparently impacted because the system had indications the brakes were in use.

It has been suggested to me that left-foot braking may exacerbate the problem when it occurs. I don;t know if this would be the case, although there is obviously more likelihood of simultaneous brake and throttle actuation.

The car was returned today ater a rapid turnaround. So far so good, and hopefully this is fixed.

bronson7

Thank you for the update. Let's hope it's a forgotten issue.

allans

I had the EXACT same issue with my 2016 GT3. They also diagnosed it as a brake light switch and replaced it. It did NOT cure the problem. Don't own the car anymore. Hope you have better results. Best, Allan

Banango

Allan: same code? I will observe the car with interest and merge with slight trepidation!

R.Deacon

Banango , Thanks for educating here of your cars malfunction , and hopefully diagnosis is correct

and the fix is good ; drive on and hopefully you can continue to keep on driving : without recurrence

allans

Sorry didn't note the Code but, my issue was just how you described yours. Again, hope yours works out well. Best, Allan

sgroer

Is there any possibility this is the reason you don't own the 2016 anymore Allan?

downhillracer

I have had the same problem for 15 months on my 2015 GT3. Identical symptoms and it seems very dangerous to pull out and have no power.

I have had the brake cylinder and switch replaced and it did not help.

On my car the problem is 100% related to left foot braking, simultaneous brake and gas positive pedals.

Since I quit left foot braking it never happens anymore except when I accidentally left foot brake.

I have no record of the error code, if any, the dealer found. I have had the car in for this 4-5 times.

It is going back to the shop next week and i will push them hard on this. Maybe my new brake cylinder was defective also

John

allans

Nope.

levd

I have a similar issue.

Dealer re-calibrated PDK, but nothing changed.

Today Macca showed me this thread and I discovered there's one thing in common, seems like most if not all of us, having this issue, are braking with left foot.

I switched back to right foot braking now and hope it will be ok this way. Today everything worked perfect with RFB.

downhillracer

levd,

I am positive that my problem is 100% related to left foot braking. Sometimes i accidentally touch it while backing down the driveway while lightly touching the throttle. As soon as I move forward I can feel the hesitation in the engine. I have found that if I shut the motor off and restart it everything is fine.

But it is still dangerous, if I accidentally left foot brake at a stop sign or light without realizing I did it, I have virtually no power upon acceleration.

One of the tech from Porsche North America came to Houston to specifically look at my car. He returned with all the car data to analyze. Eventually they replaced the brake cylinder and the stop light switch. It still does the same thing.

I have looked back at my service invoices and a do see a trans reprogram and I know they have refreshed all the software several times.

One of the service invoices says
"5611 read faults and create val. report known issue to PCA. repair is being refined and will be available soon."
Dated February 15, 2016

John

levd

Ouch, that's really bad.

With my car the effect is much, much smaller. Sometimes takes days of LFB driving to notice.

downhillracer

I got my 2015 GT3 back from the dealer and it is finally fixed. Tried every combination of left foot braking and other foot on the accelerator I could think of and never felt the hesitation from a standing start.

As I mentioned earlier I already had the brake cylinder and stop light switched replaced but it did not solve the problem

This time my fault code was P0524 indicating DME version 2698 software. The software was upgraded to 3271 version and the problem is gone. I think the software number is specific to the engine - DME

There is a Technical Bulletin concerning this exact problem that indicates the software was released March 29, 2016.

Interesting that the Bulletin discusses a fault Code of P0571 which I did not have.

Hope this helps someone else who has had this really annoying problem.

John

Banango

FWIW, I have not had any further incidences of the issue since the repair and software update. That includes two track days. I have not been left foot braking, but have three track days coming up later this month and will likely use my left foot. We shall see...

levd

My issue never appeared back so far since I gave up LFB.