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Problem with PSMS

I am writing to tell you of a recent experience with my 991 (Gen 1 2013) whilst driving to Braunton, North Devon for Christmas.

Approaching Bristol the Porsche Stability Management System (PSM) warning light came on advising me that the PSM was not working, but I could continue to drive if careful. I did not stop and continued on my way, but after fifteen to twenty minutes the car started to behave erratically with the PDK downshifting to apply engine breaking and resisting attempts to accelerate.

I exited M4 and found a layby where I could gather my thoughts. I called Porsche Assistance who said they would send a recovery vehicle to take me back to OPC Reading. They told me that the recovery vehicle would take approximately two hours to arrive. While, waiting I tried the fuses for the PSM (Passenger footwell). Both checking them for failure and also cleaning the contacts. In the poor light no fuses appeared to have failed

After fiddling about in the cold and dark I tried starting the car. It started and without the PSM warning light. Consequently, rather than miss Christmas in Devon, I called Porsche Assistance and cancelled the recovery vehicle. I was soon on my way again and got as far as Taunton Deane services on M5 before the PSM warning light reappeared. I stopped for a break and repeated the fiddling with the fuses thing again in the hope that, that was where the problem lay. Once again, the PSM warning light did not reappear when I started the car.

I was on the North Devon link road (A361) approximately three quarters the way to Braunton when the PSM warning light reappeared. I stopped again and fiddled with the fuses. Again when I started the car the warning light had disappeared!

This time I got to the outskirts of Braunton before the PSM warning light reappeared. I limped into Braunton with the PDK behaving erratically and the PSM warning light on and managed to get the car to my brother's house, where it remained over Christmas. 

I called Porsche Assistance again and arranged to have the car recovered to OPC Reading on Wednesday 27th and a courtesy car delivered to me. The return journey home in the courtesy car, a Mercedes E220d, in the dark and snow, also was not without event, but that's another story.

Kirston Edworthy was my contact at OPC Reading and he provided daily updates on progress with my car. My description of the symptoms and the diagnostic download was sent to the Porsche boffins in Stuttgart for analysis.

Their response was that the problem lay not with the fuses, but with a bushing on the brake pedal! When hot the bushing expands and the pedal does not return fully to the off position The PSM senses this and when applying the accelerator there is a conflict. Is the car braking or accelerating? Braking is the safer option and the PDK downshifts to apply engine braking! Hence, the erratic behaviour.

The problem with the bushing is a known design fault and the bushing was replaced under an extended warranty.

My thanks go to all those at OPC Reading who were involved in getting my car back on the road.

Barry Setterfield

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