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The cheapest fix to try is to replace the 2 boards. I would do that first.
Following up on this, I took advantage of a few fairly mild mid-40s New England days during Christmas week and performed the removal of the Mechatronic unit and replacement of the PCB-1 and PCB-2 boards using Mechatronics Repair Kit 0B5398009F.
With the Macan up on stands, I drained the 45,000 mile old fluid, which was very clean, with no sludge on the pan bottom. There was a tiny amount of very fine gray sludge on the magnets.
The job of removing the Mechatronic unit went fairly smoothly, with the only point of difficulty being the removal (and subsequent re-installation) of the external transmission filter. Pulling it straight down, off the two very rigid steel lines while simultaneously pulling it out laterally from the opening in the side of the transmission proved to be a difficult affair. Equally frustrating was putting it back on.
Once out, and with the old boards off, I ohm'd out the various solenoids, which were all in spec. New PCB-1 & 2 boards were fitted, internal transmission oil pipes were replaced with new, internal suction filter was replaced, all gaskets/o-rings/bolts were renewed and the pendulum swung back the other way with re-installation of all components, culminating with appx 6.5 liters of fresh LIQUI-MOLY Dual Clutch Gear Oil 8100. I will say, I have noticed the shifts since the LIQUI-MOLY fluid change are next-level smooth, and a huge improvement over how it was prior.
But more importantly, and it's been a week now, the “Gearbox fault - Possible no R-gear. Drive on possible” warning along with the P174000 (Clutch temperature monitoring) and P17D800 (Torque limitation due to clutch temperature) codes have not returned!
I have to give a huge shout-out to Andy Buck's Masterpiece DIY on the job, in which he, in very exacting detail, outlines every single step of performing this job on the DL-501 transmission from beginning to end. A tremendous resource that I just had to mention.
And thanks @VAGfan for the fine resource you are, and for your valued participation on this thread, in this forum and beyond! I do want to test the old PCB-1 & 2 boards I removed, specifically the PCB-2 and Clutch Oil Sensor G509. Hoping to find the "smoking gun." Do you know how exactly I can test this with my DMM? In a past post from 11/2022 (#235 of this thread), you mentioned the clutch fluid sensor is bad if it has an open circuit. Does that mean if I pin it out with the appropriate connector slots (which are 3 & 4 for the PCB-2 connector), there SHOULD be continuity if it's good, and if there's NO continuity it's bad? FWIW, it ohms out to 1.067 k/ohms (which, from what I’ve gathered is reasonable), but it's an open circuit continuity-wise when pinned out.
Great job, glad you got it fixed.
With the DMM meter set to OHMS (Resistance) range, the clutch fluid temperature sensor (around room temperature) will read about 10,000 Ohms ("10K"). If the sensor is bad, it will read over 20,000 Ohms ("20K"), or way below 10K Ohms. The problem could have been an intermittent open circuit in the board wiring, from the actual sensor element (a thermistor) to the pin of the plug-in rectangular connector (at the end of the wire harness). The above resistance ranges for Good/Bad are my guess, based on typical NTC thermistors that I am familiar with. NTC thermistors have a high resistance when cold, and a low resistance when hot.
Concerning your DMM measurement, if you actually got 1067K Ohms (1067,000 Ohms), that is a bad sensor.
Concerning your DMM measurement, if you actually got 1067K Ohms (1067,000 Ohms), that is a bad sensor.
I just checked again, and it appears I omitted the decimal, so it reads 1.057 k/ohms, which should put it in spec, correct, which would support your theory of a weak link somewhere between the sensor and the connector.
Now that I've had occasion to test the original PCB-2 board (from the mechatronic unit of my 2015 Macan S) to the best of my rudimentary abilities, I believe I have found the 'smoking gun' I was in search of.
The operating specs on the G509 Clutch Oil Temperature sensor (part of the vertical PCB-2 board on the DL-501 mechatronic unit) are:
@ 30°C ~ 1.13K ohms
@ 100°C ~ 1.38K ohms
I aimed a heat gun at the sensor on the PCB-2 board and watched the multimeter as the temperature came up to the 100°C (212°F) mark, where I adjusted it and held the temperature. My findings as it rose, and at a few points within the 60-80°C mark, were that the multimeter would intermittently flash an "OL" (open circuit), on and off, which eventually stopped as the temperature rose higher, with the ohm reading at the 100°C mark being 1.426M ohms — yes, megaohms. I'm no engineer, but I believe that to be well out of the window, and the on and off open circuit warnings would explain the in and out flashing gearbox warnings, which ultimately led to my replacement of the two mech boards. Since replacement a few weeks ago, there have been no more codes.
I put together a little graphic of the connector pins for the PCB-1 and PCB-2 boards and their relation to the various solenoids and sensors on the mechatronic unit, if one would like to test the pin connections from the connector to the individual solenoid connections on the mech board and sensors.
I hope the info I provided along the way will help those who follow with similar mech issues.
And, correcting my earlier post, the room temperature reading of the temperature sensor should be around 1 K (1000 Ohms), not 10 K (10,000 Ohms) as I had stated earlier. Standard values for thermistor temperature sensors are typically 1K or 10K at room temperature.
Too bad you didn't measure the new temp sensor, before you installed it.
Interesting. That specification (~20% increase in resistance across 70C) is somewhat unusual. You can get both PTC and NTC thermistors but in temperature sensing applications, NTC is much more common, providing reduced resistance as the temperature goes up. And usually there would be a resistance decrease of 5x or more at the hot end of the range.
Makes me think it's not just a simple thermistor, but something that needs more support circuitry to return a meaningful reading. In any case there are a ton of fault reports associated with the G509 sensor, so it sounds like a genuine problem area.
Hey Guys - I’ve got some experience w these DL501 transmissions and Mechatronics units. I’ve served the Audi c7 community (c7s have the same trans) for the last 4/5 years in finding solutions and selling oem mechatronics repair kits. If anyone needs one I’d be more than happy to provide you with one. Feel free to send me a msg and let me know if yall got any questions or issues. Cheers
- Most common parts that fail are either solenoids or the boards. All this stuff sits inside the transmission hot fluid, and over time they just go bad and start sending wrong info to the tcu/ecu. There’s certain ohm values that they have to be within, and when they go out of those parameters they start acting up causing faults, safe mode and issues.
-Yes this is a complete kit and i also send DIY instructions how to fix it yourself. All you need is a lift and it’s fairly easy if you are somewhat mechanically inclined. And yes, Any reliable shop should be able to perform this repair.
Last edited by ComponentHaus; 05-17-2024 at 02:59 PM.
Ok so I think this is going to be me also joining in with the conversation on my 2015 Turbo. I'm hoping to just try the electronic repair kit first. Is that wise??? Is there a full cost estimate for your kit?
Ok so I think this is going to be me also joining in with the conversation on my 2015 Turbo. I'm hoping to just try the electronic repair kit first. Is that wise???
01-05-2024, 12:33 AM
