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5HP18 & MS41.2 Transmission Flashing

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  • #16
    Originally posted by bmwstephen View Post

    Pulled from a 95 m3

    95 tcu by Stephen Chen, on Flickr

    but keep in mind. 1995 automatic was using the s50/OBD 1 and a 3.23 diff so it maybe specific to that engine configuration (vs s52/OBDII and 3.38 diff)
    I'm tempted to say that's definitely the difference- but now I'm hesitant to say that the early OBDII cars also use the GS8.32.

    I'll verify mine at some point if I can stop being busy with repairing damage from animals running out in front of me every night....


    • #17
      Originally posted by bmwstephen
      Also have this spare module lying around from an s52 manual (vin verified). Bosch GS8.32. So both manual and automatic of the s52 appear to use the same module. I am betting the difference is the actual eeprom chip inside.

      304903658_10160190854387463_321661340071286192_n by Stephen Chen, on Flickr
      Hold up, that's....odd?

      A automatic transmission computer is vin matched to a manual car? I can't think of what purpose it'd serve - are you sure the car is a factory MT?


      • #18
        Originally posted by bmwstephen
        what I am saying is that both automatic and manuals use the same control module. The difference is the eeprom chip inside (or lack there of one if you have a manual). yes it is a factory manual from a 99 S52 that we parted out for a manual swap into a 1995.
        The part I don't understand is why a manual trans car would have a module soley dedicated to controlling an auto transmission - simply without the memory chip.

        The DMEs are the same- ms41.2 (marked 41.1), even the software on them as far as I know, but I don't see why a transmission control module would be found in a MT car regardless. I'm hardly an E36 expert but I can't seem to find any talk online about MT cars having the module, rather talk about unplugging and removing the entire module during a MT swap comes up instead.

        I assume most GSx.xx modules used in these cars are very similar- with the chip being the difference.


        • #19
          I am no expert, but based on a few 5 speed swaps I have helped buddies done. We actually don't swap out the TCM. Even if the car started off as an auto, we just leave the module in there because none of the swap guides ever found a need to pull it out.

          A Manual TCM wouldn't have a need for an EEPROM chip which would otherwise be used to contain shift programs well.. you're manually shifting gears.

          An Auto would need that eeprom chip because it has conditional values that electronically control the solenoid which in turn control the flow of fluid to change gears.

          I also believe the need for TCM module regardless if it was an auto/manual, was because it also served as a communication channel for other drive terrain modules. Signals from ABS, ASC-T, and Cruise control also run through it which then communicates with the ECM.

          Last edited by bmwstephen; 09-01-2022, 11:12 PM.


          • #20
            Originally posted by bmwstephen View Post

            I also believe the need for TCM module regardless if it was an auto/manual, was because it also served as a communication channel for other drive terrain modules. Signals from ABS, ASC-T, and Cruise control also run through it which then communicates with the ECM.
            This makes it make a bit more sense. Convoluted nonetheless but if it's used as a gateway then I could see that.

            ​​​They're available on ebay around $30-40 (a few above and below of course) if you're trying to get rid of it I'd be glad to buy it from you if you are willing to open it and see has an EPROM chip in it. Mainly so I can read the EPROM to start working on the definition.



            • #21
              I was scratching my head for a while here, but NOW I just had a revelation.

              Doing my swap (manual to manual) I never had the second module in my car, and it is not needed for functionality of the car- with two exceptions:

              Traction control (which has been delicately placed in the dumpster) and a proper ABS system, both of which are not happy in my simple car. I do get occasional ABS idiot light probably due to tire diameter- rears are currently 275-40/17 and fronts are 225/45-17. And these rear tires are too big and look a little silly, but were less than half the cost of the preferred 265/40 size I prefer. And the wing, especially with the wickerbill, EATS the rear tires...

              I had abandoned the traction control system, since it sucked like a black hole on the ti, so not concerned, but the M3 uses a six-wire system whereas the ti uses a four-wire system, so they would never be compatible without changing the entire chassis harness (and the Group N control module will never work in my car). BUT, now I know that the second module (is it an EGS even with a manual?) would also be required to provide the comm. gateway for the wheel speed sensors.


              • #22
                From the limited and non M3 specific info I could find, the ASC requests power reduction by the DME via two analog inputs. However, as I understand, there were many different ASC and ABS setups offered so that info could indeed be incorrect for this specific variant. It's possible later systems do it all over CAN but I'm afraid to say anything - including the use of the EGS as a gateway, without more confirmation.

                The ASC would have to connect to the EGS directly for this to make sense, I'd think - otherwise the ASC CAN messages may as well be interpreted by the DME directly. If anything, the DMEs ASC power reduction system is more versatile than the transmissions own, as it can request cylinder or timing retard independently of one another. The transmission request is seemingly only handled by timing retard.

                It's been very difficult to find information on a specific year and spec, as it typically is- especially so when looking for a transmission that most driving enthusiasts deem to be...bad.


                • #23
                  I never dug into the wiring routing as once i hit the 4-wire v. six-wire wall, I scrapped it.

                  But it seems it would make sense, if they have that second "computer" available, to use it to interpret input from wheels and brakes to pass "orders" on to the engine DME.

                  Looking back it seems to be a "band-aid", but maybe the easiest way to implement it at the time with existing Bosch DMEs, but that's speculation.