Help with 5A41 DCT fault ?

[MajorBob]

Hi, I am getting the 5A41 Pressure Sensor, Clutch 1 DCT fault. The car is is in limp mode and the fault will not clear though ISTA. I recently did a full fluid and filter service and the fault was not present before the service. The old fluid was contaminated, possibly by antifress and i replaced the Transmision Fluid heat exchanger as a result. Fluid is now clean and pure. There are no other faults on the car. Im 99% sure the level is topped off and its not a low fluid issue. Any thoughts on things to check or what to troublshoot? ISTA says its likly the Mechatronics but i want to exhaust all options before going there. Thanks in advance for any ideas.

[BayAreaE93]

Using ISTA, rerun all the transmission learn-in procedures, including the clutch adaptations, mechatronics adaptations, and torque curve adaptations.

Did you run the oil-balancing procedure after you filled the trans with new fluid? This is crucial to attain the correct level of trans fluid after doing a drain and fill.

[MajorBob]

Thanks for the response! Yep, did the ISTA oil balancing, also the ISTA Trnz flush and Clutch, Mech and Tourque adaption. Clutch adaptions returns a faulty cluch message and the tourque adapt. would not complete for some reason. Ill try re-running them tomorrow but starting to suspect that the presure valve for clutch 1 may be cloged or blocked. Next step may be removing the Mechatronics and throughly cleaning it or finding a replacement.

[MajorBob]

Just attemped to re-run the adaptations, still no luck. any thoughts?

[deansbimmer]

Did you replace the high pressure filter?

You may have accidentally rolled the o-ring when reinstalling the sump filter.

PV faults usually end up with a replacement mechatronics. No point in attempting to Clean the sensors- they're not accessible for service. Replacing the Mechatronics is not a trivial or inexpensive matter as they're VIN locked.

[MajorBob]

thanks, I did roll the sump filter o-ring :-(. Rechecked it Sunday and finding it so, i thought i may have found the issue. replaced with a new o-ring and confirmed it was correctly seated and sealed, but the fault remains. Sounds like im in need of a new Machatronics and i guess some coding

[MajorBob]

So I’m going to remove the Transmission this weekend and first thoroughly inspect the wiring harness. I found this post :
https://www.m3post.com/forums/showthread.php?t=1290327
and having experience with my M5's SMG transmission know firsthand how brittle the wiring can be. If i find something suspicious i will repair and replace the tranz. If not my next step is going to be to remove the mechatronics unit and inspect it. I may separate the valve body from the electronics and thoroughly clean it. I figure there is no harm trying since at this point my next option is a new mechatronics unit.
Question, does anyone have a link to a DCT wiring diagram?

[BayAreaE93]

Originally Posted by MajorBob

So I’m going to remove the Transmission this weekend and first thoroughly inspect the wiring harness. I found this post :
https://www.m3post.com/forums/showthread.php?t=1290327
and having experience with my M5's SMG transmission know firsthand how brittle the wiring can be. If i find something suspicious i will repair and replace the tranz. If not my next step is going to be to remove the mechatronics unit and inspect it. I may separate the valve body from the electronics and thoroughly clean it. I figure there is no harm trying since at this point my next option is a new mechatronics unit.
Question, does anyone have a link to a DCT wiring diagram?

I've heard that often times if the mechatronics unit is found to be faulty then it is more common to replace the entire trans with a remanufactured unit, I believe the mech unit itself already runs $5,000+

[MajorBob]

Yep, and thats where this may end up. Unfortunatly though the complete DCT is a bit harder to come by for my car. Its a 2012 135i and is only a direct swap with another 1 or 3 series with the same trans. The M3s are a little different which is odd becouse just the mechatronics unit is interchangable to all.

[spammysammich]

My nephew has the same car and the DCT in his feels quite a bit different than mine. I'm running a Dinan tune and have a LOT more miles. His transmission feels a lot more smooth, as if it slips the clutch more often on down shifts. A lot more like a traditional auto feel puttering around but lightning fast changes when hustling.

Good luck with the exploratory work and repair.

[MajorBob]

Got the tranz out today, no obvious wire issues but will examine it more closely as soon as i have some free time. Dam, i wish i had a higher ceiling and a real lift :-(. The quick jack is great for most routine maintenance and repairs but this would have taken half the time with a real full lift (and a second set of arms).

Any thoughts on what to inspect or check? Obviously the internal connection to the mechatronics, but has anyone gone further? I’m thinking there is no harm in digging in here since the next step is probably a new mechatronics or DCT, if I can find one.

Thanks for any input or sugestions.

[Helmsman]

Wow, big job!
Bob, Stripclub made some findings that might be of interest as you have the box out: https://www.m3post.com/forums/showthread.php?t=1772232

[MajorBob]

thanks! that’s a good tip. I had not planned on inspecting the clutch or the wiring behind it but i guess since I’m this far...

[MajorBob]

Spent a couple hours closely examining the wiring harness, disconnected all the connectors and cleaned contacts with electrical cleaner, checked the relays and fuses in the ebox. could find nothing obvious or suspicious. DCT connectors seems fine and wires are pliable and not brittle. Moved on to the DCT its self. Opened the Mechatronics and removed the clutch cover. fluid under the mechatronics looked like the same Pepto bismal that poured out the first time i drained the DCT a month or so ago. Some also poured out when i removed the clutch cover. After some carful cleaning i still could find nothing obvious. I won’t remove the clutch but was able to inspect behind it with some small inspection mirrors and am satisfied its ok and all the fasteners are secure.

Next step will be removing the mechatronics. Based on the condition of the fluid i would not be surprised if some of the valves are either clogged or otherwise compromised. I’m still very hopeful that a thorough and careful cleaning will resolve the pressure sensor failure for clutch 1. If anyone has any suggestion on other areas to inspect please let me know.

Thanks!

[Helmsman]

Originally Posted by MajorBob

Spent a couple hours closely examining the wiring harness, disconnected all the connectors and cleaned contacts with electrical cleaner, checked the relays and fuses in the ebox. could find nothing obvious or suspicious. DCT connectors seems fine and wires are pliable and not brittle. Moved on to the DCT its self. Opened the Mechatronics and removed the clutch cover. fluid under the mechatronics looked like the same Pepto bismal that poured out the first time i drained the DCT a month or so ago. Some also poured out when i removed the clutch cover. After some carful cleaning i still could find nothing obvious. I won’t remove the clutch but was able to inspect behind it with some small inspection mirrors and am satisfied its ok and all the fasteners are secure.

Next step will be removing the mechatronics. Based on the condition of the fluid i would not be surprised if some of the valves are either clogged or otherwise compromised. I’m still very hopeful that a thorough and careful cleaning will resolve the pressure sensor failure for clutch 1. If anyone has any suggestion on other areas to inspect please let me know.

Thanks!

Good luck.

Should you not have bumped into these BMW DCT documents you may find them useful at some point:
M DCT desciption: https://www.m3post.com/forums/attach...4&d=1317583307
Fluid service: https://www.e90post.com/forums/attac...6&d=1532477767

Cheers

[MajorBob]

Thanks for the links Helmsman! very handy. Weird that the failure is my odd gears but, reverse is working, and reverse is supposed to be part of the odd gear set. That’s why I’m starting to lean to an e-box or fault in one of the valves.
I removed the clutch yesterday and inspected the clutch disks, they all look surprisingly good. Bit of a pain reinstalling, especially without the special tool, but i improvised and got it done. Pictures of the discs and behind. Everything behind was nice and tight and no loose bolts.

[Helmsman]

Originally Posted by MajorBob

Thanks for the links Helmsman! very handy. Weird that the failure is my odd gears but, reverse is working, and reverse is supposed to be part of the odd gear set. That’s why I’m starting to lean to an e-box or fault in one of the valves.
I removed the clutch yesterday and inspected the clutch disks, they all look surprisingly good. Bit of a pain reinstalling, especially without the special tool, but i improvised and got it done. Pictures of the discs and behind. Everything behind was nice and tight and no loose bolts.

So no need to replace the clutches while you're in there Bob? What is the mileage on the box btw? (fluid was bad?)

[StripclubDJ]

FYI

DONT get the snap rings mixed up

[MajorBob]

Thanks for the tips! Yep, I think the clutch is fine, Box has 85K, and the friction surfaces seem clean, good depth and no indication or damage or burning. The fluid was contaminated with coolant due to a leak in the Transmission Fluid heat exchanger. That’s been replaced but some of the contaminated fluid was not flushed when i changed the fluid afterword’s. I’m pretty sure this disassembly will get any that’s left :-)

FYI - The visual error i was getting was the one on page 53 of the M DCT Drivelogic download. I believe this correlates to the ISTA fault also - 5A41

Ill post some more pictures when i examine the valve body

thanks!

[Helmsman]

Originally Posted by MajorBob

Thanks for the tips! Yep, I think the clutch is fine, Box has 85K, and the friction surfaces seem clean, good depth and no indication or damage or burning. The fluid was contaminated with coolant due to a leak in the Transmission Fluid heat exchanger. That’s been replaced but some of the contaminated fluid was not flushed when i changed the fluid afterword’s. I’m pretty sure this disassembly will get any that’s left :-)

FYI - The visual error i was getting was the one on page 53 of the M DCT Drivelogic download. I believe this correlates to the ISTA fault also - 5A41

Ill post some more pictures when i examine the valve body

thanks!

Ah, first time I've heard of coolant leak into the DCT oil. Did you also notice oil in the (engine) coolant expansion tank Bob?

[MajorBob]

No trans fluid in the coolant which doesnt surprise me considering the greater pressure coolant is under when it heats up. Im sure the leak was very small, and since we dont have an easy way to check it (no dipstick) it could have been buiulding up for a while. Disclaimer: Ive only put about 20 miles on the car since getting it last december. It needed a multitude of things fixed before i could even drive it. The first time i ran ISTA, there were 37 faults, now im down to the 1. Replacing the DCT fluid was the very last thing i did before driving it for the first time. After a couple drives where it was running great, i got the DCT fault :-(

[MajorBob]

Short update. I remove the electronics portion of the mechatronics. Pretty easy as it mounted on top of the valve body and held in place by a dozen or so Torx screws. I found someone on eBay who sells used ones. They are guaranteed good and he re-codes them with your existing unit which I’ll send Monday. He seemed pretty confident that the pressure sensor, mounted on the E-unit is the culprit. This make sense to me also based on the fault and the lack of any obvious issues in the clutch. Valve body seems fine and i checked each of the solenoids and they all seem to function properly.

It will probably be a couple weeks before i have the new unit back, mounted and the DCT ready to install. needless to say, my fingers are crossed!