Odd gear clutch slip/no reverse *Error Code 5A5B* Update 12/3

[BeaterM3]

Weird thing just happened.

Driving normally in Drive mode DCT, shift aggression at 5.

Was in 3rd gear and then suddenly the RPMS kept climbing and climbing - not shifting. It got up to 7K and I had to let off the throttle. RPMS came down. It stayed in 3rd gear though and when easing on the gas, the RPMs again kept climbing and would not shift to 4th.

The way the car was picking up and how the RPMs were behaving from 4k to 7k, it almost felt like the trans software glitched and thought it was in Sport/Manual Mode and kept hanging on the gear.

I then threw it into Sport mode, the aggression was at 3 and I had control over the shifting again. I pulled into my work's parking lot and put it back into Drive mode and drove around the lot a bit and the shifting was back to normal, no increased or high revving in 3rd, just the normal Drive mode pick up.

Also, no error codes popped up. No limp mode. no check engine. The DCT was just looked at in July 2019 and the bottom pan and gasket were replaced and new trans fluid was added.

Anyone else ever have this happen?

[BeaterM3]

No one?

[DJiGGs]

think you answered your own question....maybe for some reason the car was switched into manual mode but was showing it was under auto...
try to replicate the problem if you cant then it sounds like it was a one off.

[BeaterM3]

Well on the drive home i think i may have diagnosis this...on all the odd gears and reverse i get hesitation, jerkiness and spiking rpms. Not in the even gears.

Im thinking it may be a clutch issue in the odd set of gears.

[BeaterM3]

Hope this is easier and less expensive to fix then the clutches.

Looks like there is an SIB out for this code.

SI B28 01 09
Double-clutch Transmission with Drivelogic March 2009
Technical Service

This Service Information bulletin supersedes SI B28 01 09 dated March 2009.

designates changes to this revision

SUBJECT
M3 with M DCT – Gearbox Warning Lamp with FC 5A87, 5A81 or 5A5B


MODEL
E90, E92, E93 M3 with S65 and M DCT transmission produced up to 03/09


SITUATION
The customer may complain that intermittently, the red "Gearbox Emergency Program" indicator is displayed in the cluster or in the CC. The fault codes 5A87 ("Internal Transmission EEPROM data"), 5A81 ("5V Internal voltage failure"), or 5A5B ("Control valve PV7") are stored in the DCT transmission control module.

The vehicle's drivability is not affected by this condition.

CAUSE
Erroneous faults caused by the diagnostic software error in the DCT transmission control module

SOLUTION
In case fault codes 5A87/5A81/ 5A5B are stored, clear the DCT fault memory and allow the vehicle to enter sleep mode. Stored fault codes should be erased. Release the vehicle to the customer.

In the unlikely event that the fault codes and the transmission warning lamp return after performing the above procedure, contact Getrag TeileClearing via the PuMA case titled "M3 M DCT – FC 5A87/5A81/ 5A5B".

The improved DCT software, which eliminates erroneous faults 5A87/5A81/5A5B, is planned for release in March 2009 (ISTA/P 2.33.0).

WARRANTY INFORMATION
For information only

[BeaterM3]

Time for an update.

So diagnostics show the clutch and clutch pressure sensors are GTG.

The issue looks like it may be coming from the mechatronics ...

I have read that the wiring in the mechatronics can get brittle over the years and break/snap/etc and with the exception of that 1 trans code that never came back, the trans hasn't been throwing anymore codes while in the shop. I am crossing my fingers it is the wiring. If not, looks like I am on the hunt for a used or rebuilt mecha unit.

[BeaterM3]

deansbimmer

Hey I came across a post made to another member regarding the 5A5B code. Do you have any other info you have come across since the OP (2017)?

[djsilverjohnson]

If it was mine I would start by going to a trusted dealer and find out if you have the latest update or need the update mentioned above. (SI B28 01 09) If it does have that update, then I would look into the condition of the wiring harness before looking for a replacement mechatronic unit or transmission. In other words, with multiple possible causes, I would start at the cheapest and work up!

[BeaterM3]

Originally Posted by djsilverjohnson

If it was mine I would start by going to a trusted dealer and find out if you have the latest update or need the update mentioned above. (SI B28 01 09) If it does have that update, then I would look into the condition of the wiring harness before looking for a replacement mechatronic unit or transmission. In other words, with multiple possible causes, I would start at the cheapest and work up!

Thanks for the reply.

My mechanic (who has an amazing rep for his work) already tried the software update. Didn't fix the issue. The wiring in the mecha is the next thing to be checked ... which I mentioned regarding the brittle wiring ... I am crossing my fingers it will be wiring.

[deansbimmer]

Originally Posted by revengeismine

deansbimmer

Hey I came across a post made to another member regarding the 5A5B code. Do you have any other info you have come across since the OP (2017)?

No. It's too time consuming and usually not financially economical to repair these. Anytime these DCT have problems, and it's rare that they do, it's cheaper and faster to replace the trans rather than repeatedly pull the old one to replace parts and troubleshoot. Good used DCTs can be found for as little as $1000.

[BeaterM3]

Thanks for the replies.

It ended up being the Mechatronics unit. I was going to look into a full trans replacement but I found a steal of a deal on a working low mileage Mechatronics unit that I went with purchasing.