mdvigil

We will try that once the parts arrive. I also ordered another TCU, just in case.

mdvigil

The new valve body arrived today... damaged. The two solenoid heads on opposing ends were crushed. Thankfully, we kept the old valve body and replaced the broken solenoids. Initially, I attempted to purchase a refurbished valve body from Sheng Hai Auto Parts to be economical. However, after I was informed that the valve body was in stock, but not in stock, had to be tested, and failed testing, I requested a refund. I purchased the new valve body from Goldcrest Parts.

We installed the valve body and a new Dodson transmission filter, wiped the TCU, and the codes cleared. Today we will refill the PDK with fresh fluid and see if we can rerun the calibration. Fingers crossed.

mdvigil

@PV997 We filled the PDK with fluid and started the car. When we put the shifter into drive, the dash will show it is in first gear (it did not do this before), switch to second, and then stay flashing in fourth. Still no wheel movement. We decided to watch for values while the car was running, and we found that pressure regulators 1, 2, and 7 values are at 0. When first started there will be values and then drop to 0. Any idea on the wiring schematic for these sensors? We are certain this is the issue. Any help would be greatly appreciated.

PV997

The wiring goes from the TCU to the PDK connector closest to the engine (there are two connectors). From there inside the PDK the harness fans out to the pressure sensors and the solenoids (pressure regulators). Check the main post in the valve body section as I list the connectors, pin outs, and expected resistance. You can buzz them out at either location.

Pressure regulators 1 and 2 are for clutch 1 and clutch 2 which probably isn't a coincidence. In your screen shot you can also see the clutch pressure sensors are both at 1 bar (atmospheric pressure) which seems consistent with what you are seeing (i.e. no clutch engagement). I stripcharted my clutch pressure rowing through the gears awhile back and the disengaged clutch was at 1 bar and the engaged clutch was between 4 and 10 bar. So for whatever reason, the clutch just isn't engaging. It could be a wiring open/short or it could be that the TCU isn't commanding it for some reason.

What's the year and model? I'm not sure what pressure regulator 7 as the later models added additional regulator(s) for things like a locking differential and I'm not clear on the numbering for those.

mdvigil

@PV997 Thanks for the response. My mistake for not replying to mention that we found the post with the needed wiring diagram information.

We found a loose connection, and now all the sensors are reading values, but still no clutch engagement. All other codes have cleared except P1765 (gear disengagement lock). We think it may be the distance position sensor. We have a couple more tests to run, but we are fairly certain this may be the issue.

The car is a 2014 turbo s.

PV997

Nice, I've got a 2010 turbo that I've been thinking about beefing up myself. I know the PDK clutch is the weak link, but with the Dodson what's the torque limit? The factory stock turbo clutch is 700 NM according to ZF IIRC. Anything else need to be upgraded in the PDK?

BTW, I've attached the troubleshooting flow diagrams to this post in case you don't have it. Unfortunately for P1765 by itself its says "contact the importer" which isn't much help. If other codes start showing up it might be useful though.

mdvigil

@PV997 Not entirely sure about the torque limit. Dodson advertises their clutch will hold up to 1300 hp. From what Sam at ByDesign has told me, unless the build is crazy, the Dodson clutch is good enough for most builds. Once we get this transmission issue sorted, our build should be around the 1000ish hp range. We also switched the factory LSD to a Wavetrac unit.

I reached out to T-Design. They relayed that they have not seen P1765 associated with a distance sensor failure. They do not have this code in their database. They mentioned sensor range is usually P1731 to P1735 and /or 1735-36. And sometimes just 1706. So this may not be our issue. Now we are thinking it may be an internal fault in the clutch. No other codes have presented. We cannot run the recalibration because the code will not clear.

mdvigil

@curt3g How did you resolve the P1765 issue?

PV997

I still suspect it's something with the TCU. When you said you wiped it what did you do?

mdvigil

So, we pulled the PDK and found this... hydraulic gear that drives the PDK pump. After replacing the valve body with the updated version and ordering the distance sensor from T-Design, it turned out to be a mechanical issue. Ordering a new gear from Dodson. We plan to replace the distance sensor since we already have the part and, in doing so, decrease the likelihood of a future failure of this sensor. I guess we'll have an updated PDK once we're done. Thanks, to everyone for the insight, wisdom, and suggestions.

PV997

Glad you found something. As a systems engineer obsessed with recognizing patterns, I always try to understand how something happened and why it caused the symptoms it did. I'm having a hard time correlating that damage with what you observed. Any thoughts on why it was causing these faults? Hopefully it's not debris from that damage trapped somewhere in the hydraulic system. As to how it happened, perhaps the clutch was misaligned when mated to the PDK?

Randy90266

@PV997, Intermittent failure described my issue exactly. Zero issues with PDK for the first 15-20 minutes after a cold start, but would throw faults and default to 7th gear thereafter. A 45 minute cooldown on the side of the 405 and I could get approximately 5 miles before the PDK would fail again. Thanks to T-Design and Beck's European, it's an issue I no longer have to deal with.

mdvigil

@PV997 We have a theory.

First, the cannon plug to the distance sensor was not fully turned and locked.
Second, when the hydraulic gear sheared off, the metal shavings contaminated the valve body causing the implausible signal codes.
After we replaced the valve body, the implausible signal codes cleared, but the P1765 code remained. When we started the car with the new gear installed, the code was still present until we put the car in drive and the wheels started to move. The messages on the dash resolved, and the code disappeared.

It seems like a cascade of events contributed to the various fault codes. It is difficult to discern what occurred first. However, from the other posts I've read, it seems that similar symptoms (e.g., clunking noise, loss of wheel momentum in drive or reverse when put in gear) and faults occur when this gear fails. We believe the gear was not fully seated on the clutch pack causing the failure.

Dodson sells this gear. It is relatively affordable at $1k, and the PDK is not too difficult to remove. IMO it is worth checking this gear failure when commensurate symptoms occur rather than replacing the PDK.

PV997

Thanks for the update and what you say makes sense. One of the things we've seen is that when the TCU encounters something unexpected (like you describe from the shavings) it throws odd codes and locks functions out. These obviously won't clear while the problem is still there, but they often won't clear even after it's been fixed. If you read old posts from when people had their PDK transmission replaced, you'll often see the dealership/garage also had to replace the TCU also to get it working. I suspect that was overkill and the TCU only needed to be wiped and refreshed, but most dealerships just throw parts at things rather than actually try and figure out what is going on.

notfastenough

Exactly why we do oil analysis before removal and teardown if we get odd codes. At least it helps us get some idea what to expect ahead of time.