ECU, PSM, Auto Start/Stop Fail Symptoms --> Bad Coil
Just wanted to give a head's up to the 981 crowd about the failure modes for coils.
I was driving along on my daily commute and about 20-min in, all hell broke loose. It started with a PSM fail message, followed a few seconds afterward by an ECU fault and Auto Start/Stop fail message. Car started running like crap - felt like I was driving over serrated pavement. I limped on to work and set on to figure out what to do next.
The first thing that popped into my mind was maybe a faulty battery - it is 4 years old and it's consistently in the high 90's to 100's in Texas this time of year - perfect recipe for a failed battery. I've heard these symptoms are typical for that. I pulled into the lot at work and turned off the car and tried a restart - still running like crap and the fail messages reappeared.
I decided to wait until lunch, let the car cool, and maybe the problem would go away temporarily for me to get home and pull the codes. At lunch, the car started right up. Check engine light was still on, but the car was running fine. I decided to give it a try to make it home to pull the codes. About the same thing happened. It was great on the freeway, but after about 20 mins as I slowed down at my exit, the warning messages re-appeared and engine started running like crap again.
Limped home the remaining 2 miles and pulled out the code reader. A lot of codes - several PSM comm fail messages, cyl 5 misfire, cyl 5 soft shutdown - now I knew why it was running lousy - it was only using 5 cylinders. I don't have the code readout in front of me - I'll add the full set of codes I pulled later.
I had changed the plugs about 8K miles ago, so I was fairly sure that wasn't the problem. My next guess was the coil. I had hoped that Porsche had perfected the coil-on-plug design since the crappy coils on my 2004 Mazda 6, but alas, I guess not. I'd put quite a few high-temp track days on the car this spring, so I'm guessing that contributed to the (pre-mature?) failure.
Long story short - cylinder 5 coil.
Looks like they have redesigned the coil since the late-2013 production run for my car. Latest coil is a rev-07. I'll probably plan to replace the full set later this fall when it cools off. I was talking to another 981BS owner and he indicated PCNA replaced his entire set under warranty after a second coil failure. So, it sounds like this may be a common problem.
2014 Boxster S - Racing Yellow, Sport Chrono, PASM, PTV, PDK, 3rd radiator, Cobb Stage 1 tune (Pagid RSL29's & Nitto NT-01's on the track)