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Thread: Are 402 DMEs Different for Automatic and Standard Transmissions?

  1. #1
    Join Date
    Feb 2018
    Location
    St Louis, MO USA
    Posts
    12
    My Cars
    1995 M3

    Are 402 DMEs Different for Automatic and Standard Transmissions?

    Lent a friend my 1992 325i sedan and told him not to wash it because i had the DME cover off. He washed it. Did tell me. Then let it sit. Then it wouldn't start. No good deed goes unpunished. I removed the original red label DME (FE04256 10/91 standard transmission) and replaced it with a silver label 402 DME from another 92 325i sedan (FF90037 02/92 automatic transmission). Car won't start. The issue I'm having is that the fuel pump relay pin 85--which is a the ground coming from the DME (only active when key is on)--is no longer grounding. If I jump the fuel pump relay the car fires right up. I'm wondering if that has something to do with installing a DME from an automatic car into a standard car.

    If they are different can I swap the chip from the original or have the new one coded or something?

    Thanks!

  2. #2
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    No expert here. But I think you're right. I think the automatic DME expects the transmission to send a signal that it's in park, before it will allow you to start. I think all you have to do is make the DME think the transmission is in park, and you're good to go. Might need another simple hack. Perhaps you could reflash the DME with a manual-DME eprom, or just plug a manual EPROM in your DME. Not sure if you can swap EPROM between red-label and silver-label DMEs, but otherwise you could swap the eprom from your soaked manual DME into the silver label DME. I think it should be possible to just swap it (if the EPROM wasn't soaked, but if you let it dry, it will probably even work, not very high-tech those EPROM chips).

    But not 100% sure.. Best if someone with more experience could confirm.. I don't have much experience with automatics because I don't like them. Out of the 20+ BMWs I had, only a E32 740iL had the automatic (sold it quite soon after; the automatic did sort of match the V8 and E32 chassis, but it was understeering like hell, and was a way too heavy car with all heavy options like double glazing, gasoline burner to pre-heat engine/coolant and stuff; was a nice experience though; quite off-topic though ;-) )

    Update: Not sure, but perhaps your new DME just has a bad connection at the pin that drives the fuel pump.. I think an automatic DME should fire up normally in a manual car. At least in the https://www.bimmerforums.com/forum/s...on-Swap-Thread (auto-to-manual swap) thread they don't mention any work that needs to be done to the DME or to the wiring..
    Update 2: Oh, wait, here it is: My first thought was probably correct: You'll need to supply ground to one of the DME pins I think, to make the DME think it's in neutral or park: #36 . Which pin: it should be written down somewhere on the internet. Or you have to look it up in the Bentley manual.

    Easiest solution: Just try and swap the EPROM from the manual DME to the automatic DME, and I think it will instantly turn into a manual DME. Not much work, just make sure you don't bend the aluminum tabs too far, or they will break off. And gently remove the EPROM without bending its pins, and note the orientation (little indent on one side).
    Last edited by ed323i; 01-21-2019 at 06:37 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  3. #3
    Join Date
    Jul 2018
    Location
    Denver, CO
    Posts
    50
    My Cars
    1999 BMW 328is
    I'm not expert in this, but when I manual swapped my OBDII e36, I didn't have to change anything, computer wise, to make it TURN ON. only issues that I had with using the automatic DME was that it TRIED to hold RPMs whenever I'd clutch in, and it would idle high (950rpm) as it was anticipating an extra load of a torque converter. I drove it on the auto ECU for months until i finally got my performance tune with my m50 manifold swap and had it coded to manual.

    Also, the engine computer shouldn't matter. The transmission computer is separate. When you look in the compartment, the actual engine computer sits on the "lower level." the transmission computer, while having the same harness, has much less wire going to it and is bolted to a bracket on the "upper level."

    sorry if the obdii cars are different in this manner than the obdi, but there's that.

  4. #4
    Join Date
    Feb 2018
    Location
    St Louis, MO USA
    Posts
    12
    My Cars
    1995 M3

    Problem Solved

    I swapped in a DME from a manual trans car and everything seems to be working fine. Thanks for all the help!

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