I am posting this for anyone who may have this problem in the future and to save them the multiple hours that I wasted fixing this issue. Typically, the "ignition lock faulty" dash warning is caused by the well known water infiltration problem which corrodes several splices in the wiring harness that runs along the left-hand side front floorboard. This was not the issue in my case.

The problem arose after I had removed the instrument cluster to replace the LCD. I was feeling good about how quickly and efficiently I had performed the repair. That feeling quickly turned to dismay when I turned the ignition key and got the "ignition lock faulty" warning on the dash. This fault is especially frustrating as it means that the OBDII port is completely dead (I tried the "hold the brakes 30 second trick" and it would not wake up). Turning the key does nothing. So a scantool is useless here.

Did I jostle some fragile connection that was about to go when I was fiddling inside the dash? Maybe I placed my foot on the wiring harness that is known to go bad in just the right way to finish it off. I checked all the fuses. Pulled the Kessy fuse (41, left side of dash) and pretty much every other fuse. Checked both batteries. Split open the the floorboard wiring harness and inspected the splices. They looked almost as good as new, although I went ahead and redid them with solder and heat-shrink tubing. Checked the 433 relay on top of the battery. Checked a number of other various things. I determined that the steering column lock was not receiving power from the Kessy. For some reason the Kessy module was not signalling (pulling low) the term 15 actuation signal line (pin A58). Well that's strange, I thought. The steering lock receives power from the Kessy, but the power comes from term 15, fuse 26, which is routed back to the Kessy (this is the way I understand it). So since the Kessy wasn't activating term 15 power, it wasn't receiving back the power needed to power the steering column lock. OK, there's something wrong with the Kessy.

So I pulled the Kessy and started poking around. I checked the IRFZ24NS mosfets in the corner of the board. ~200 ohms gate to source, 0.2 Vsd on one. Yikes, that's bad. It hadn't blown the associated resistors yet though. The other one was ~700 ohms gate to source, 0.7 Vsd. Not as bad but still sucky. I looked around for the extra mosfets I bought the last time I replaced them about 8 years ago. I couldn't find them so I reassembled the Kessy and installed it back in the car as I didn't see anything else out of the ordinary. The mosfets shouldn't have anything to do with the problem anyways. I did order some more replacements and will put them in next week.

When I reinstalled the Kessy the warning went away! Problem fixed. My theory is that somehow the Kessy module got into some weird, nonfunctional state when I disconnected the instrument cluster. Even though I had pulled the fuses, and even the battery lead (I didn't do the secondary battery though), apparently the Kessy hadn't gone unpowered long enough to fully reset.

So anyways, if you get an "ignition lock faulty" and it isn't the typical wiring harness issue, try disconnecting the Kessy for a full 5 minutes or so.

 

I'm just sooo glad I did not get KESSY....

 

I have a 991.2 (2017) and it get a "Steering lock fault"...(think it's the same as your "Ignition lock fault"). Today for the first time (gotten the fault 2 or 3X before but no issues) I accidentally turned the car off instead of the headlights...then the car wouldn't start! I'm sitting in the middle of the road, past the guard's gate, and trying to start the car! It was like a dead battery but it's good. What's your "KEESY"...I'm thinking it's the remote access or whatever it's called...a silver "key" fob thing in the key hole instead of the actual key.
sometimes I do get a "can't find key" message but it always (so far) has worked when I move the key in my pocket.
Eventually the car did start (after hearing many sarcastic "Nice car" comments as people drove past me). It MAY have been the 5 minutes you mentioned.

Thanks for the suggestions "So anyways, if you get an "ignition lock faulty" and it isn't the typical wiring harness issue, try disconnecting the Kessy for a full 5 minutes or so." I'll have the shop look at that harness.

 

So I've been having this issue, but with no fault or anything showing up on the dashboard. It simply powers up the radio and instrument panel saying "Porsche", but will not engage the starter or allow the gearshifter to move.
I was dreading an ignition lock failure, but pulled the Kessy fuse and it push it back it. Fixed the issue.

It happened again a day ago and same thing. In my records for the car, the steering ignition was replaced not too long ago with a new unit.

My question is where do you think I should start to try and fix this intermittent issue? If pulling the Kessy fuse resets it, is my Kessy module starting to fail? Can I pull that and get the mosfets re-soldered?

Thanks a ton!

 

My '06 CTTS has been trouble free...well, especially since I scrapped the PCM for a Pioneer head unit (Still using OEM amp and Bose Speakers). At 105k I've redone the suspension (75k), and replaced the Driveline around 55~60k but now just did the JXB Performance Center Support bearing carrier. Did the Air Compressor rebuild (Ebayer BagpipingAndy). Kessey has been fine as well as dash LCD's? Those seem like more work than wrenching on the suspension or wiring in my stereo (BTW, still have use of Steering wheel buttons with the Crutchfield kit and Bose sounds better than with the PCM). Will it eventually happen to all Cayenne's? Are my days numbered? Love my Pig, had it since '08.

 

This thing has been relatively trouble free. I have a Stage 1 Tune on it which has given it a nice little "boost". Oil consumption is well within specs.

Really just this odd issue which pulling the fuse fixes. I have noticed if I leave my cig. lighter adapter plugged in it tends to happen.

Maybe it's pulling enough amps to pull the battery voltage below 12? The adapter has a voltage indicator on it and I'm only seeing 12.0 volts when i do start it. 13.5 when running at idle.

Perhaps the battery is slowly dying? I've pulled the rear battery covers off and it looks fairly new.

Luckily I have records for the past 20k miles of work (control arms/KESSY fix). So it seems odd to me a new steering column would have issues only 2 years later 🤷

 

The KESSY board re-work is something I ordered the parts for (I believe 6 speed online has a write up with pictures) that may be worth looking into. Unless you already had record of someone replacing the components on the board? Stupid things in my mind that float into focus; what diagnostic system do you use? A couple will give you a read on the antennas, maybe there's an intermittent issue there? I know for me, the failure of the seal in one of the door buttons causes the key to occasionally vanish from the car (while remaining in my pocket) that may be an issue at play? Can't think of other non-destructive tests to perform and with my own soldering skills the last thing I'd trust myself with is replacement of the known bad components on the KESSY module.

 

I just have the iCarsoft Por-II reader (2 of them). Had one for my Cayman and the gentleman I purchased the car from gave me one.

I have tried to look at specific DTCs, but haven't necessarily found anything. Obviously I think getting a Durametric will be worthwhile.

If the steering column was replaced by Speedometer Solutions, I would assume they fixed the KESSY. Gotta be something else right?

 

You mentioned a KESSY fix there, there are two 'failure points' in the steering column lock, the actual mechanism in the steering column which can go bad, and the actual KESSY control module which is located in the dash to the right of the steering column. They might have asked for both the module and the steering column mechanism (and then fixed both) but I remember them being different services offered. I'd trust your records over my guess work based on nothing here :-)