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Thread: Motronic 1.3 using E34 harness...Is it long enough for the e23?

  1. #1
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    Motronic 1.3 using E34 harness...Is it long enough for the e23?

    Hi All,

    I am ready to begin the installation of the Motronic 1.3 components in my '85 735i. I have rebuilt a harness from a 1990 e34 535i. Does anyone know if the harness is long enough to reach the glove box? I would like to place the ECU there below the ABS computer. I had the thought of creating a new entry point for the harness in the firewall in front of the glove box however all the refrigerant lines for the A/C seem to be in the way. Looking at the harness length and the distance it needs to travel to reach the glove box using the existing harness entry point (near the right fender) I am a little skeptical of it reaching. I would like to know what have others done.

    Thanks, Eric
    84 528e
    85 735i
    03 530i



  2. #2
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    It's not long enough to reach, short by a good stretch. Wait for Jay535is to chime in, or hitman X, they will give you solid advise.
    Last edited by kojo96; 07-21-2017 at 06:16 PM.

  3. #3
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    Thanks! Looks like a solderfest is in the works! Arg!
    84 528e
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  4. #4
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    [QUOTE=pennybond;29777333]Thanks! Looks like a solderfest is in the works! Arg![/QU

    Yup, Like 53 wires and 18" in length needed to extend, that's from memory but remember Jay telling me-

  5. #5
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    I'm chiming in...
    No matter what harness you use, none are long enough.
    You will need to extend by about 18", and I found it easier to use the end from a 1988 528e harness since it put the ECU connector and lock in the right orientation relative to how the ECU mounts.
    This becomes a full afternoon or all day project, just because of all the stripping, cleaning, soldering, heat shrinking, and taping of the entire harness. (just in case this isn't clear, don't try and solder in an 18" extension-that's madness-solder on a new end from another harness)
    I did this on my euro 735 a few years ago, the 10:1 really prefers 1.3.

    I highly recommend stripping the entire harness, make sure each connector ohms out, and wrap with new tape. Carefully cut the firewall grommet from the original harness, and re-glue around the new harness.
    Also, create a power wire from the battery to the starter, then take the power for the ECU/relays from that top start bolt instead of all the way from the battery, looks much cleaner.
    There is a relay holder from the E30 that will hold the relays you need, and mount near the harness entry point.
    There is also a diagnostic plug holder from the E30 that holds it beautifully, these things really clean up the engine bay.
    Don't forget to think about the lack of CSV, you can delete that and its fuel line, make sure you have the 'A' thermostat housing with a plug for the thermo-time switch you also won't need, and make sure you install the bracket for the front timing sensor BEFORE buttoning up the timing wheel :-)
    I have a nice PDF with all the pins and colors, I think in my signature.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  6. #6
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    Hey Jay,

    Thanks or chiming in! I appreciate the knowledge. Looks like I need procure a few more "tidy up" items you mentioned above.

    I have not been looking forward to the process of all that soldering and your suggestion of another harness connector is interesting. I did come across these little guys on Amazon this weekend and ordered some. Supposed to be quicker than traditional soldering, uses a heat gun and water tight too. What do you think?https://www.amazon.com/dp/B01ILSEDWI...=2WLKMZL6UJAA1

    I have already unwrapped and mostly re-wrapped the harness and created a sub-harness that incorporates the alt to starter line, blue alt trigger wire and oil level sender wires. All pins currently ohm out.

    Attachment 605857

    My CSV is already disconnected from both power and fuel as I believe it was a little leaky. The Thermotime switch is also removed and plugged.

    So a question on your power wire suggestion. The "new" power wire from the battery to the start would terminate on the top bolt of the starter? Do you suggest this to then be able to run power wire to the ecu/relays through the harness making it hidden? I ask because I looked at the wiring diagram for the starter and see that it is terminal 15 and looks to be energized only when the starter is operating. So it would just be used as a mounting post?

    Thanks again,
    Eric
    84 528e
    85 735i
    03 530i



  7. #7
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    Please don't use those crimp terminals, you will regret not taking the time to do it right.
    The soldering sucks, I'm not gonna lie about it, but its the right way to do it.

    You can do without the triangulation of power wires, just make sure you have new wire from the battery to the alternator and starter. Take the power for the relays from the alt to starter lug, I'm probably visualizing it wrong while sitting here at my stupid desk at stupid work...

    You can probably acquire a new harness end from a car at Pick N Pull, or just grab an entire spare harness for ends/terminations.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  8. #8
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    Ok so tap the big lug on starter where the alt cable and battery cable connect to the starter for constant on power.

    Also, the connectors I referenced above actually have low heat solder in the middle of them (middle ring in picture) and sealer adhesive at each end. No crimping involved.
    Are you still leery of this product even though they are not crimped and in fact soldered?

    I had originally planned to solder all the connection so it is not a big deal if I have to go that route...just more time consuming. I want to do it right, either way!
    84 528e
    85 735i
    03 530i



  9. #9
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    Hmm, I admit that as soon as I saw what looked like heat shrink butt connectors, I immediately closed the window and huffed and puffed... :-)
    Those look interesting, and have good reviews, but something to consider is how bulky that section with all the joints is going to get, like a Boa that just ate an antelope. You probably won't be able to feed that section thru the firewall, so would have to plan accordingly.
    I'm just a fan of solder with a nice mechanical wire bond. Its tedious but it's strong and doesn't grow to be a huge bundle when you have 50+ joints.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  10. #10
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    They are intriguing, are they not! One thought I had to handle the bulk is to offset the splices a bit and maybe do 10 or less in the same area and them shift down a bit mixing with some traditional solder joints too.

    My connector arrive tomorrow so I'm gonna get started tomorrow night after work. I'll let you know how it goes!

    Thanks for all your help, Jay!
    84 528e
    85 735i
    03 530i



  11. #11
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    Did you obtain the harness extension? Perhaps I missed it.
    Measure, measure measure before you cut and solder anything. Lay the harness on the engine, see where it will go thru the firewall, and make sure you don't get your splices too far in.
    This may be elementary to you, but all too often it seems people ask these questions without thinking things all the way thru. I just try and help with all the eventualities I can assist with.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  12. #12
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    Hey Jay,

    No you did not miss it. I did not procure an additional ecu connector section. I am going to double my effort and just extend what I have, call me crazy??? Yes, I know but I am hoping these solder connectors will speed the process. And yes I will be cognizant of the "Boa factor" and the firewall!

    Question:

    Do you think it is wise to install an inline 30A fuse in the power wire from the battery?

    I believe I have seen others that have like demetk over on mye28.
    Last edited by pennybond; 07-27-2017 at 12:03 PM.
    84 528e
    85 735i
    03 530i



  13. #13
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    My concern with using generic wires to extend the harness is with the shields.
    And yeah, I think you're nuts for doubling the amount of connections! ;-)
    I don't think it was mentioned, but which TPS are you using? The auto TPS is a great piece.
    -AND- if you have an EH auto trans, you MUST use the TCU and all the wiring between the TCU and ECU/TPS, I have seen it a few times where things just wouldn't work, until the full 1.3 TCU setup was installed.
    If you have a standard, non-EH transmission, the ECU will treat it like a manual, but you can still use the auto 6 wire TPS, just use the 3 wires that don't go to the TCU.
    ...
    Man I hope that stream of consciousness rambling makes sense...

    RE: fusing the power wire to the ECU/relays...couldn't hurt...demetk is a smart guy, and hasn't steered myself or anyone else wrong yet.
    Last edited by Jay535is; 07-27-2017 at 02:25 PM.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  14. #14
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    Jay, when you say shields do you mean the wire sheathing or are there some wires that are shielded (magnetically?) I ask because it see that there are about 4 bundles of wires (each contain about 4 wires) that go to the ecu connector that are wrapped in a black sheathing. Or is your concern with the longevity of the actual sheathing on generic wire?

    As for TPS I have a manual trans so I did not opt for the 6 wire auto TPS.

    Don't worry about stream of consciousness.....the more info the better!

    I actually laid out the harness over the top of the engine last night to take some measurements and I think I'm going t extend about 24 inches so I have some wiggle room to position the ecu in the glove box. Also that should be long enough in case I want to leave the ecu in the speaker well.

    I still have tasks (other than wire extensions to complete like wiring in the square C101 connector and wiring in the oil level sender. But I'm still driving the car so I'll wait until I get the harness extended to do those.
    84 528e
    85 735i
    03 530i



  15. #15
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    The thicker black bundles are actually individual coax cables, with a stranded wire shield around an inner jacketed wire core. They are considered grounds, so should have continuity.

    The 6 wire TPS is a more robust unit, and doesn't wear out as easily as the 3 wire, so if you have a harness from an auto tranny car, acquire the 6 pin TPS.
    Take more time that I did with the oil level sender, I wired mine backwards and now it always reads low...been too lazy to get in there and reverse it. Not sure if its reversed at the sender, or the harness splice. :-/
    I see that you are also an E28 owner, the E23 C101 is different so make sure you don't use the wrong diagram!
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  16. #16
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    I thought that might be the case....Hmmm, do you have any shielding ideas? Do you remember what they are for? I'm thinking O2 sensor, maybe ABS? Isn't ABS a separate harness on the e23?

    I'll keep my eye out for the auto tranny TPS and plug but the harness I have has the manual connector wired in currently.

    I guess I did not realize the e23 C101 is different than the e28. That means the C101 Motronic 1.0 to C101 Motronic 1.3 wiring diagram is useless to me! Is there one out the on the web for the e23 or can I figure it out from the wiring diagrams?
    Last edited by pennybond; 07-27-2017 at 07:02 PM.
    84 528e
    85 735i
    03 530i



  17. #17
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    message me with your email and I can send you what you need.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  18. #18
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    Hey Jay,

    I sent you a private message however it did not appear to send. So I'll post it here:



    Thanks again for the diagrams you sent. They have been invaluable coupled with the ETMs!

    I had a couple of questions now that I have liberated the old Motronic 1.0 out of the engine bay and make final preparations for putting in the new harness.

    1) There appears to be no need for the O2 sensor heater relay which, in the E34 535i, is now tied in with the Fuel pump relay making it a dual purpose relay of sorts?
    2) The 179 ECU (M 1.3) has an input for vehicle speed, Pin 29, (from the Speedo) which the 059 (M 1.0) does not. Do I need to run a wire from the cluster to ECU Pin 29 for this input?
    3) I have about 10 wires that are coming from the Motronic 1.3 round C101 that are not used. A few like tach, econometer, O2 Sensor heater relay (if 1 above is true.) are accounted for as “not used” so that leaves about 7 that are not.

    Others wires not used in addition to above:
    Check Engine light
    Vehicle Speed signal from cluster to Pin 29 on ECU (If #2 above is true I can take wire from cluster (Speedo) to this wire?)
    Unloader relay, (does this need to be hooked up?)
    Diagnostic connector (Pin 6 on Diagn. Connector)
    Wire to Pin 17 on Round connector
    Wire to Pin 19 on Round connector
    Wire To pin 20 on Round connector. Diagram says ABS Power.

    I hope I am on the right path.

    Thanks for your help!

    Eric
    84 528e
    85 735i
    03 530i



  19. #19
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    I've been watching this thread. You won't regret the 1.3 upgrade, it's a lot better than the older system. I just got done with a similar project on mine, my chassis was an '86 E24 (1.0 adaptive) with a '91 E34 535iM harness (1.3) using an '82 E24 (1.0 Basic) Euro engine harness added. I'm not sure how much I can add, but here goes:

    The shielded coax I knew about are from the crank & cam senders, likely the O2 signal as well.
    The O2 heater relay wasn't required on mine; the diagrams said it should be installed, but I never found it. The O2 works just fine as far as I can tell.
    That VSS input is an odd one. I don't think I hooked it up. I've heard that the speedo conditions the diff signal, then sends it back to the DME. I dont know why, perhaps to improve fuel efficiency or to run a vehicle speed limiter? Could also be required for the automatic transmission or the traction control/EMS electronic throttle.
    On the older cars, the tach & econometer are run directly to the DME through the C102 plug. It's a small white plug (usually three pin) in the DME harness. I didn't wire them up in the C101, just spliced them directly into the harness near the DME connector instead. I'm sure C102 will be in your kick panel, I can take a pic later today unless you've already wired it up. I'm told some cars also have A/C signal wires in that connector.
    I will run a check engine light over to the gauge cluster eventually. I temporarily have it wired up in the engine compartment right off the C101 instead. Wiring for that light is odd. If I recall correctly I ran a wire from battery +, to an incandescent light, then to the C101. LED wouldn't work, always stayed lit.
    I also ran into a little trouble with the temp sensors (use the 1.3 DME temp sensor and a SuperEta temp sender for the gauges)
    I'm still trying to figure out the static/dynamic oil level sender. Everything else seems OK.

    Best of luck!

  20. #20
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    Hey Dave!

    Thanks for the added info. I was able to deal with the shielded coax with some copper tape with conductive adhesive I found on Amazon and some rubber electrical splice tape from Home Depot. I have continuity on the shielding so that is good.

    I did read that others have also said that the O2 sensor heater relay is not needed as the fuel pump relay supplies that function. (And the 1990 e34 ETM has 2 diagrams for this circuit; one for the 525i with a heater relay and one for the 535i which just uses the fuel pump relay.) So I feel confident there.

    On the VSS I had your same thoughts about its function/use. IF it is for fuel efficiency I'd like it to be there. But if it is from EMS or auto trans than I don't need it.

    For C103 or C102 as you said above I did find this connection. I clipped it from the old harness and spliced it into the 1.3 harness. Mine is 3 pins where I think most other cars are 5 or 6 pins. Pins 1 and 3 are the signal for tach and econometer and pin 2 is switched power from the ignition switch I think through the OBC relay to take advantage of the code feature on the OBC for starting. (I bypassed this a long time ago to not suffer from the no start condition that can happen.) So my current question is do I need to splice pin 2 into the harness to get switched power to pin 27 on the ecu? The wire goes from pin 27 on the ecu to pin 9 on the 1.3 C101 and then I have it wired to pin 10 on the e23 C101 which is labeled as switched power unfused. I'm just wonderinfg if power is coming from that direction as well or if it only flows from the direction of C103 pin 2?

    I was going to use my current b34 coolant temp sensor as it is a Bosch and only a few months old. I believe the b34 and b35 use the same sensor. I also did purchase the super Eta temp sender for the gauge cluster.

    The dynamic and static oil level circuit was a bit confusing at first as the wire are opposite between the b34 and b35. You just have to compare the 2 ETM diagrams. I ended up cutting off the round connector and wired in a bosch fuel injector type connector like used on the 1.3 harness.

    I feel I'm getting close!

    E
    84 528e
    85 735i
    03 530i



  21. #21
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    Awesome! I'm glad you're on top of all the snags. If you've done all that soldering my hat is off to you!

    I didn't splice pin 2 on the C102. Didn't make any difference at all. I'm not sure how the circuit is designed; I would figure that it doesn't use any power to disable the DME.

    I'll take another crack at the oil sensor, thanks for the advice. I'm using the 1.3 3-pin Bosch connector too. Believe it or not, my '82 Euro fuse box plug doesn't have the correct pin to meet the '85 fuse box.

  22. #22
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    I realize this thread has been inactive for some years, but does anyone have the c101 pinout or the motronic 1 to 1.3 document from Jay535is' signature? working on MS wiring at the moment and hoping I dont have to wade thru the electrical troubleshooting pdf. Thanks!

  23. #23
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    Shoot me an email or PM

  24. #24
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    PDF from Sig

    Quote Originally Posted by Jay535is View Post
    Shoot me an email or PM
    Any chance I can get the File fro your Sig on the 1 to 1.3 wiring? I am converting a 733i to megasquirt and struggling to parse the two harnesses with the electronic troubleshooting guide from each. It would be a huge help.

    Thanks

    My Email is feyrerm@gmail.com

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