VAGfan

Olddragger
Do you still have the old Mechatronic unit? If so, could you send it to me for an "autopsy"?

Olddragger

Be glad to. I will send a private message for your address etc.

BCCarrera2

I too am having trouble with the PDK in my 2017 Macan Turbo with 85K miles. PDK service, (fluid/filter change) was performed at 48K miles. In September/October 2022 I had a few weeks of occasional rough shifts in 1st and 2nd at stoplights etc. Got the “Possible R gear fault driving permitted” warning in the instrument cluster. Took it to Porsche Bellevue and they quoted me $6700+tax to replace the “transmission valve body” but said it probably really needs full transmission replacement. Transmission replacement was their strong recommendation. For this they quoted $26,500 +tax. They reported faults P17D400-clutch valve in gear train half 1 – mechanical fault and P17D800 – torque limitation due to clutch temperature. I paid the $300 diagnostic fee and drove it home.

I ordered the “slide valve gearbox” part number 9A7-325-025-01 from Sunset Porsche Parts https://www.sunsetporscheparts.com/o...ox-9a732502501 for $3,334 along with the rest of the necessary gaskets, tubes, seals etc. to replace the mechatronic unit and picked the order up in person, (I was already headed that direction but…yes I drove to Beaverton to save the 10.1% tax). Interestingly they also list the complete transmission for sale at $13,956 plus a $6,589 core charge.

Waited a few weeks for what seemed like the actual slow boat from China for my PIWIS 2 clone hardware to arrive, spun up a virtual machine to run the “free” software and pulled my Mech unit. Overall pretty easy in my garage on jack stands. I tested all the solenoids with my Ohm meter and all seemed within a couple tenths of an Ohm of spec. Ordered a ~$300 solenoid kit from Amazon from a Chinese reseller and replaced all but two of the solenoids in my original mech unit. Foolishly, I didn’t replace the N435 and N439 solenoids. The existing solenoids were both black and the plungers felt “properly” spring loaded and were not easily separable top to bottom. From the replacement kit one was black and one white-ish like Olddragger’s photos. The white one had a zip tie through one of the mounting holes, was separable top to bottom and seemed to be missing its internal plunger spring. I don’t think I switched these solenoids during re-installation but…maybe? Reinstalled the old mech unit with the “new” solenoids and buttoned everything back up. Performed the control mechanism calibration per the shop manual with PIWIS ( Overview -> PDK -> Maintenance/repairs -> Calibration after removing and installing mechatronics -> [F12]) without issue. Started it up dropped it into reverse to back out of the garage, no go, wouldn't move in reverse. Seemed like it would move forward but don't have enough room in the garage to properly test without reverse availalbe. Now I have P17D500 clutch valve in gear train half 2 mechanical fault. So maybe I really do have a bad clutch valve solenoid and maybe I did accidentally switch them.

Naturally I was hoping a $300 solenoid kit would save me $3k when I returned the new mech unit but…. I don’t have a replacement N435/439 solenoid and I’m not really looking forward to potentially pulling the mech unit a third time so now plan to put the new mech unit in.

When replacing the mech unit the service manual says: subsequent work > 1. Program control mechanism for transmission. 2. Teach engine immobilizer. 3. Calibrate control mechanism for transmission. 4. Code control mechanism for transmission.

So, finally, my questions.

1. Can I skip #2 teach engine immobilizer? I don’t think it’s possible to perform with a PIWIS2 clone that doesn’t talk to the mothership. Let me know if anyone knows otherwise.

2. Can I perform #4, code control mechanism?

If I can’t complete all the necessary programing, I’ll have to swap the old transmission control unit for the new one which negates some of the benefit of spending the $3k for a completely new Mech unit.

Sorry for the long post.

VAGfan

I would swap your TCU computer from your old Mech to the new Mech. I don't think the problem is with the TCU.

Did the problems only occur with a hot engine/transmission? If so, there are other people who have had this issue, and the root-cause was a leaking gasket that is located between the two metal halves of the bottom horizontal section of the valve body.
See post #224, above.

BCCarrera2

You're probably correct. Good plan. Thanks.

BCCarrera2

VAGfan. Before I tear it all apart again I'd like to make sure it isn't a calibration issue with the clutch valve. I notice in the Audi forums there seem to be lots of individual solenoid actuations/calibration procedures in the Audi software. Do you know if these also exist in PIWIS2? I'm new to the interface and it's a little cryptic.

VAGfan

I am not familiar with the PIWIS2 (or the equiv Audi) scan tool calibration procedures for the DL501.
There are some Youtube videos which show, step-by-step, how they are run for an Audi, perhaps you can use that to fiqure out the equiv PIWIS2 procedure names/titles.

VAGfan

Did your original problems only occur with a hot engine/transmission?

BCCarrera2

I had just finished bring fluid to ~40c temp for fluid top-off. Shortly thereafter tried to reverse and got the clutch valve 2 error. So, no, doesn't seem to be a "hot" issue except for the original P17D800 torque limitation due to clutch temp.

VAGfan

Genuine Volkswagen Audi - 0B5398009F - Mechatronics Repair Kit 0B5398009F (0B5 398 009 F) (ecstuning.com)

The two black plastic interconnect circuit boards are also a known failure in the DL501. Note that the vertical board also contains the clutch fluid temp, and if that goes bad (open circuit), the TCU goes into failsafe mode, thinking that the clutch temperature might be too high (since it can't read the sensor anymore). Can you read the "Clutch Temperature" with your PIWIS? (There are 3 temperature sensors in the Mechatronic).

BCCarrera2

Thanks, I'll search YouTube a little. Probably best to just replace the whole thing with TCU swap. Wife is eager to drive it again, like yesterday. I may try to recondition the old mech once it's out. Talked to a guy at the local Transtar/Transcend branch and he quoted me ~$600 each for the Sonnax tool kits to re-bore the Clutch Cooling Valve and Pressure Regulator Valve plus another ~$200 for the Reaming Fixture jig. Throw in 4 real BorgWarner solenoids, (N440, N438, N471 and N472, i haven't found a source for OEM N435/439 yet) and a gasket kit which includes solution to the failure point you reference between layers of the lower valve body and total cost is roughly $2200 and would still need new control module PCB 1&2 and Gear Selector solenoids to be "all new" like the new mech unit. Sorry, just talking myself into installing the new unit.

BCCarrera2

All three temperature sensor's data ave available in PIWIS2. Interestingly when I was bringing up to temp for fluid top off there was always an ~8C difference between the two temp senors.

BCCarrera2

PDK issues solved.

I swapped the TCU from my original Mechatronic unit to the new Mech unit to avoid coding and immobilizer concerns.

Shifts like a dream again.

Thanks to all in this thread for the invaluable info. I'm happy to provide additional info if others are interested.

VAGfan

Good to hear!

Did you run all the calibrations with the new Mech/Old TCU ?

BCCarrera2

I only performed the calibration the service manual specified. When "removing and installing the control mechanism" the calibration performed by PIWIS2 is a distance sensor calibration. The options in the PDK Maintenance repairs tab of PIWIS 2 are:

1. Calibration after replacement of sensor module (selector lever position)
a. The learning values of the transmission-range sensor are re-taught and
b. The respective stop positions of the gear actuators are calibrated (distance-sensor calibration).

2. Calibration after replacement of mechatronic components (hydraulics and control unit)
a. The learning values of the transmission-range sensor are re-taught and
b. The respective end positions of the gear actuators are compared (distance-sensor calibration)
c. The learning values of clutch adaptation are subsequently reset and the clutch pressure is taught.

3. Calibration after removal and installation of the mechatronic components
a. During calibration after removal and installation of the mechatronic components, the respective end positions of the gear actuators are compared (distance – sensor calibration)

4. Calibration after replacement of mechanical transmission components/PDK
a. During adaptation of the clutch friction points, the learning values of clutch adaptation are result and the clutch pressure required to close the clutch enough so that it just begins to transfer torque are taught.