byroncheung

Thanks for getting in touch @toddlamb , I admire the work you guys are doing with the PDK. I ended up taking the car to a shop that's closer to where I'm located and easier for me to get to, they have done a few distance sensor replacements so hope it will work out.

I spent the last couple of days going through the entire thread. I do want to pick your and other knowledgeable members' brains (e.g. @PV997 , @t-design and others...) on this - my car (a 997.2 c2s) suffered the failure right after an autocross / car-control clinic event. I have done these events and also track-days multiple times before without issues. Before this last event, I have done 2 mods on the car: I had an LSD put in the car (the car came with a factory open diff) and I also added a rocker switch to disconnect the yaw sensor completely. LSD can make the transmission run hotter, and I wonder if the yaw sensor allows the car to do something smart in protecting the transmission, e.g. maybe disengaging the clutch when it detects the car is spinning out 360, and disconnecting the yaw sensor could contribute to the transmission running hotter? During the event, I don't think I saw an error about transmission overheating, although I wonder if it is possible that the PSM failure error (due to yaw sensor disconnect) was masking an overheating message, or maybe I simply missed an overheating message if the dash was cycling between PSM failure and an overheating message. Also when playing on a skidpad, there were a few times the car shut itself off after I spun out 360. The car restarted without problem after those shutoffs (other than the expected PSM failure due to yaw sensor disconnect), but I did find it weird because I have never had the car shut down like this before, in hindsight maybe it was some sort of protective mechanism? (Obviously, it could all be just unlucky timing, maybe it was time for the sensor to go regardless of the mods, but I find the timing very curious)

Ultimately my question is, there seems to be a consensus that there is a vague/weak correlation between high temp and distance sensor failure - do we think the redesigned T-Design unit is more robust against high temp and/or track usages of these cars? Just thinking ahead how should I treat my car going forward when I got the car back on road - should I stop going to track with it, don't play with the yaw sensor disconnect anymore, go back to open diff, or look into adding extra cooling measure on the PDK (seems like there are options for Cayman but I couldn't find one for 997.2, not sure if the Cayman kit will fit for 997.2?).

Thanks for your help in advance.

vrybad

Wow, subbed for a great thread.
Very well done, OP.

Fullyield

This is my response to byronchueng’s question about whether the PDK distance sensor failure is heat related. I have followed this thread for years. While I would certainly defer to PV 997 or Todd Lamb or Beck’s European opinions as they all have much more experience than I, my two cents is that the failure is NOT heat or mileage related. It frequently occurs on Porsches that have never been tracked or heat stressed. There does not appear to be a pattern to the failures that I can see.If anything, it could possibly be age related. We are seeing failures in mostly 997.2, 987.2 and early 981 and 991.1 cars at this time. There are fewer failures in 718, 991.2 and 992 cars. The 992 cars are still under warranty so those failures could be underreported. But, if it is age related, this will change as the newer cars age. I also think the T Design distance sensor is more robust. It has a different design and I have not seen any reports of a failure of a replacement sensor. Again, my two cents and I would certainly defer to those with greater expertise as discussed above.

byroncheung

I suppose if it's age related then there is not enough time to really tell if the new replacements are more robust because they haven't been out for a long time. But anyway it took 10 years for my car (a 2012 car) to see the failure, if the replacement last to 2032 I'm happy enough...

PV997

Thoughtful comment as always Fullyfield. I suppose I may have fueled the heal-related suspicion after I noticed Porsche added a gear oil cooler in 2013 despite the fact ZF's 2008 white paper on the transmission said it wasn't needed. My hypothesis was that since the distance sensor is submersed/doused in gear oil, they added the cooler in response to observed warranty-repair failures. It could be true, or maybe it was a "throw the kitchen sink" at it approach, or perhaps completely unrelated. But for some reason Porsche thought it important to lower gear oil temps after the PDK had been in service four years, and made some costly changes to do so.

I suspect it's a combination of heat, age, inferior component quality, an obsolete design, and it's just a lousy environment for electronics to operate. T-Design has stated they use a more modern approach (due to available tech that was not available in 2008) and that certainly simplifies the sensor. Vlad has stated they use a programmable Hall Effect sensor (IIRC) unlike Porsche/ZF's Rube Goldberg-like induction pick-up coil coupled to a separate IC along with numerous associated SMT capacitors and resistors. Modern programmable Hall Effect sensors are completely self contained, there's just a lot less components that can break.

Bottom line is that jury is still out, we just don't know and Porsche isn't talking. Preventative replacement (i.e. replacing a working distance sensor with a T-design unit) seems foolish to me as despite the high visibility failures, the factory unit is still highly reliable. Plus the T-Design unit while cheaper than a new transmission is very expensive. There are literally hundreds of thousands (maybe millions) of PDK's out there, I would be surprised if the overall distance sensor failure rate is greater than 1%.

Edit: After rereading Byron's comment I did want to mention that adding an aftermarket PDK gear oil cooler seems like a pretty good move to me for cars that are tracked or otherwise taken to the extreme. These kits are aimed at 987's as the PDK is rotated 180 degrees (the differential is toward the front rather than the back) and the diff can be oil starved during acceleration. But there's no reason they wouldn't work on a 997 other than hose lengths might need to be changed. The kits I've seen replace the drain and fill plugs with a screw in fittings allowing hoses routed to an external electric pump and heat exchanger. It's pretty clever and not difficult to install.

Nano1

Owner of a Cayman R w/ PDK here. Two weeks ago, dash display showed “Transmission emergency run” in white. Did a bit of spirited driving in the AM, then parked the car and had lunch. Afterwards, jumped back into the car and started it up. That’s when the warning was displayed. No reverse or any forward gear was selectable; car had no drive. Turned off engine and tried some minutes later, but the situation remained. Repeated the sequence again after a further wait with the same outcome.

Car has just over 19k miles. PDK shifted fine during the morning drive, even when in Sport Plus mode. An indy shop owner in the group suggested removing the cables from the battery and connecting them together to reset the system in case it was just a software glitch. But the problem persisted.

Had the car flat-bedded to a Porsche dealer. The diagnosis came back late last Friday via email with the following comment: “Fault code P1706 sensor 5v reference fault, as per Porsche diagnostic flow chart, recommend replacing PDK control unit.” It being the weekend I have not had the chance to call back and talk to the Service Advisor, but this sounded like the electronics box and not the valve body unit mounted at the bottom of the transmission. Reading through the thread on the Forum it seems the latter is usually the culprit. Has anybody had the PDK electronics box in their 997/987 fail (I will post this on the parallel discussion on the 987 Forum also)? It would be great to hear from those of you with much more technical knowledge than me. Thanks!

t-design

Naturally, we have a lot of data, and we do not see any correlation between outside temps in the geographic area, or tracking the car, or mileage. There is a weak correlation with Year, but as noted above, it can be because newer car still have warranties, and extended warranties... Other than that - distance sensor failures seem completely random. And with relatively low probability compared to # of cars on the market. So I would never advise to not choose PDK because of that.

-Vlad, T-Design

byroncheung

So there is an interesting twist in my PDK plot...

When my PDK wouldn't go into reverse and threw codes including a distance sensor failure code (P1734 the 4th shift rod sensor), I was convinced my distance sensor had failed.

Since no shop around here would do a sensor replacement, I drove 4hrs to get my car to a shop that has experience in replacing distance sensors. After a week they finally get to look at my car, the mechanic tried to clear the code but he said P1764 keeps coming back and still wouldn't go into reverse. Then he did a PDK recalibration and said now it is working properly. I'm in an awkward position because there is no shop close to me that does sensor replacement, if the shop isn't this far away I'd just take the car back and drive it until PDK acts up again and figure out the next steps. But since the shop is far away I'm kinda worrying if I take the car back and the sensor error shows up again I'll have to go through the trouble of getting the car to the shop, live without the car for a period of time, etc... And I also remember reading some cases of sensor failure that the error could be intermittent at the beginning, makes me wonder if my PDK is in the intermittent phase and should I just replace the distance sensor even if the car is working after a calibration? How common are distance sensor error that shows up but the PDK recovers and lives happily after a clear/recalibration/fluid change?

To complicate the matter further, I got the error after an autocross day and a month or two before that I put in an LSD and a yaw sensor cut-off switch in the car. The mechanic is of the opinion that maybe a recalibration should have been done when the LSD was put in (I'm trying to get clarification from the shop that puts in the LSD to see if they have drained/refill the clutch/gear oil although I guess is they didn't), but I have doubt on if an LSD change (or yaw sensor cutoff) would require a recalibration and lead to distance sensor error without one...

Any thought/wisdom is appreciated.

toma nova

My summary:
2013 Boxster S with 46k miles, about 2-3k of which are track but not in the last 3 years. One instance of stuck in 6th about a year ago, was able to limp home; restart and no further issues. Now, P1733 and P1737 (luckily in the garage). Trailered to Atlanta Speedwerks for the T-Design distance sensor replacement. No issues during the repair, 80+ miles of warm / hot test drive went fine running through all shift scenarios. The next morning, the cold test drive did not get out of the parking lot: P1764 and a metal grinding noise, possibly the pump. Trans is now out and off to the PDK expert for a complete rebuild. I was thrilled to get Todd and Brian to do the sensor repair (less $) and a bit disappointed that I'm now in for the full treatment ($$$).

byroncheung

Sorry to hear @toma nova ... So that sounds similar to my sequence (distance sensor error followed by P1764) although in my case all seems to go away after a recalibration hope I have a different outcome...
Would you mind sharing who is doing the "rebuild" for you? I have read some posts mentioning P1764 with valve body/solenoid replacement, do you now know what exactly went wrong with the PDK from your rebuild?

toma nova

Rebuild currently underway, will know more about root failure in the next couple of weeks. @toddlamb uses a local PDK expert - worked for ZF and retired from his own transmission shop, now rebuilds PDKs as a hobby. Getting new clutches, valve body, solenoids, and sensors.

A common link may be that my recalibration took several tries, failed at ~95% several times before finally taking hold. Odd that test drives while warm were good but the P1764 showed up when cold.

byroncheung

@toma nova Interesting. My shop didn't mention they have to recalibrate multiple times but I'm not 100% sure, so I'll check with them.
Thanks for sharing who/where is doing your rebuild. So the cost of a rebuild is lower than getting a new/used PDK replacement?

toddlamb

Yes the cost to rebuild is still far south of a new PDK, and it will be less likely to have issues down the road. For those with the desire, it also opens up the option to add HD clutch packs.

t-design

Multiple tries at recalibration is completely normal. I know the cases of 7 and 9 times. All on the road for a long time now!
PIWIS 3 is not advised for calibration, though. PIWIS 2 is preferable

-Vlad

docdrs

This is an interesting PDK video shot by a Netherlands shop. Just to add another PDK issue, hopefully not similar to the IMS fiasco!!! Just remember there are many PDK running flawlessly after many miles.