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Thread: MS3Pro to M50TU Adapter

  1. #1
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    MS3Pro to M50TU Adapter

    Hello all,

    I've posted in the Tuning section also, but it seems that the FI section is more active, and we likely wouldn't be tuning if we weren't going FI, SO.

    For my E34 Turbo project, I have an MS3Pro, a gutted case with an 88-pin connector, stock coil drivers, and a universal harness for the MS3Pro. I've found a number of threads for building an adapter harness for the MS3x and M50TU, but none for the MS3Pro. During my attempt at building a pinout, I'm running into issues finding where exactly grounds are supposed to go. I've read the the sensor grounds are different than the rest in that they don't go to earth?

    In older posts for the MS3x, such as goathumpers, all of the grounds on the 88-pin were connected to a single spot via ring connector, along with the grounds from the MS3x. Is this how it's supposed to be done for the MS3Pro also or do the grounds from the MS3Pro connect to individual pins on the 88-pin?

    My pinout: https://docs.google.com/spreadsheets...gJBjOg/pubhtml

    Thanks in advance!

    IMG_20180511_162536.jpg
    Last edited by CallMePuff; 05-13-2018 at 12:12 PM.

  2. #2
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    Hey! That stuff looks familiar. Glad to see its being put to good use.
    Last edited by jakermac; 05-13-2018 at 10:36 PM.

  3. #3
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    Quote Originally Posted by jakermac View Post
    Hey! That stuff looks familiar. Glad to see its being put to good use.
    It's been a slow roll so far, but I'm finally (attempting) to get this thing set up!

  4. #4
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    Sensor grounds are exactly what they say, grounds for sensors that require grounds. Cam and Crank sensors are the most important to do this with.
    1997 328is - Mishimoto Rad - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, GM Flex Fuel sensor, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Corsa Exhaust

  5. #5
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    Quote Originally Posted by somebody5788 View Post
    Sensor grounds are exactly what they say, grounds for sensors that require grounds. Cam and Crank sensors are the most important to do this with.
    Excuse my ignorance, but does that mean it's kosher to connect all of the grounds from the 88-pin to one spot and connect all of the relevant grounds (sensors, cam, crank) to the same spot?

    Sent from my Nexus 6P using Tapatalk

  6. #6
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    Quote Originally Posted by CallMePuff View Post
    Excuse my ignorance, but does that mean it's kosher to connect all of the grounds from the 88-pin to one spot and connect all of the relevant grounds (sensors, cam, crank) to the same spot?

    Sent from my Nexus 6P using Tapatalk
    Cam position and Crank Position when they have their own ground should be grounded directly to a sensor ground with nothing else grounded on that wire. Same goes for any factory sensor that is grounding to the computer. Sensor grounds are grounds for sensors and nothing else.
    1997 328is - Mishimoto Rad - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, GM Flex Fuel sensor, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Corsa Exhaust

  7. #7
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    There are 2 types of grounds in this case, like SomeBody posted.

    1. A power ground- this is the MS3pro grounding. Think of this as an output
    2. Sensor ground- this is intended to use for sensors that need a ground. Think of this as a input.

    As many power grounds should be used/grounded as possible.

    Also, remember what your trying to do with a ground, which is completing a circuit, which means your trying to get back to the negative of the battery. This can be done grounding through the car, but alot of times thats not good enough.
    328i Sedan Twin s366's, 6.0LS, TH400, MS3 Ultimate
    9.20 at 150 on 22psi

  8. #8
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    Quote Originally Posted by dburt86 View Post
    There are 2 types of grounds in this case, like SomeBody posted.

    1. A power ground- this is the MS3pro grounding. Think of this as an output
    2. Sensor ground- this is intended to use for sensors that need a ground. Think of this as a input.

    As many power grounds should be used/grounded as possible.

    Also, remember what your trying to do with a ground, which is completing a circuit, which means your trying to get back to the negative of the battery. This can be done grounding through the car, but alot of times thats not good enough.
    Both you and somebody have added great insight!

    Since this will be an adapter where the MS3 connects to the pins on the 88-pin connector which connect to the wiring harness, will the ground wires from the MS3 be connecting solely to ground pins on the stock harness?

    As far as I've seen, there are never ground wires from the adapter going to their own spot on the car.

    Sent from my Nexus 6P using Tapatalk

  9. #9
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    All of the brown wires are grounds to chassis. Also the brown with orange stripe I believe too.
    1997 328is - Mishimoto Rad - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, GM Flex Fuel sensor, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Corsa Exhaust

  10. #10
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    Quote Originally Posted by somebody5788 View Post
    All of the brown wires are grounds to chassis. Also the brown with orange stripe I believe too.
    Awesome! Thanks a ton. I also just got a Bentley manual, so I'll confirm that info.

    Sent from my Nexus 6P using Tapatalk

  11. #11
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    Ive done it both ways. Using all the factory grounds and then taking them out of the 88pin and grounding them separate. I didnt notice a difference, but if you run into issues, this is where id look first.
    328i Sedan Twin s366's, 6.0LS, TH400, MS3 Ultimate
    9.20 at 150 on 22psi

  12. #12
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    Quote Originally Posted by dburt86 View Post
    There are 2 types of grounds in this case, like SomeBody posted.

    1. A power ground- this is the MS3pro grounding. Think of this as an output
    2. Sensor ground- this is intended to use for sensors that need a ground. Think of this as a input.

    As many power grounds should be used/grounded as possible.

    Also, remember what your trying to do with a ground, which is completing a circuit, which means your trying to get back to the negative of the battery. This can be done grounding through the car, but alot of times thats not good enough.

    If I'm understanding this correctly, Power grounds from the MS3Pro will be connecting to a pin on the stock harness that goes to a chassis/battery ground while sensor grounds will connect to a pin that receives the grounding end of a sensor. In the MS3Pro's case, I see only 1 Sensor ground pin/wire. The rest of the available grounds are Power grounds. Are these okay to wire to the sensors' ground pins on the stock harness or should all sensor grounds be connecting to the one sensor ground pin/wire on the MS3Pro?

    In your thread from 2015, your pinout shows one sensor ground from the stock harness going to Pin 7 on the MS3x, which is a sensor ground, then the rest go to "spare grounds" which have no wire color. I'm a little confused about that also.

  13. #13
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    Ideally, youd make the 1 sensor ground goto a lug that you can attach all of ur sensor grounds too (do this for your 5v Ref, youll thank me later when you wanna add a pressure transducer or something)

    If that doesnt work for you, using power grounds as a sensor ground will work fine. Ive done in alot.

    What you dont wanna do is connect a sensors ground to the chassis or negative of the battery.
    328i Sedan Twin s366's, 6.0LS, TH400, MS3 Ultimate
    9.20 at 150 on 22psi

  14. #14
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    Quote Originally Posted by dburt86 View Post
    Ideally, youd make the 1 sensor ground goto a lug that you can attach all of ur sensor grounds too (do this for your 5v Ref, youll thank me later when you wanna add a pressure transducer or something)

    If that doesnt work for you, using power grounds as a sensor ground will work fine. Ive done in alot.

    What you dont wanna do is connect a sensors ground to the chassis or negative of the battery.
    So the "sensor ground" is an output to ground the MS3Pro's connected sensors to the chassis. Meaning the sensor ground pin on the MS3Pro is only directed to a ground on the chassis?

    Sent from my Nexus 6P using Tapatalk

  15. #15
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    Sensor ground is an input into the ECU from a sensor. A power ground is an Output, but both sensor and power grounds are connected internally. Im not exactly sure what makes them different, but i know they are connected (a simple continuity check with a meter will confirm this)

    If you can use ur sensor ground for a sensor, use a power ground. Dont ground a sensor to chassis.
    328i Sedan Twin s366's, 6.0LS, TH400, MS3 Ultimate
    9.20 at 150 on 22psi

  16. #16
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    Quote Originally Posted by dburt86 View Post
    Sensor ground is an input into the ECU from a sensor. A power ground is an Output, but both sensor and power grounds are connected internally. Im not exactly sure what makes them different, but i know they are connected (a simple continuity check with a meter will confirm this)

    If you can use ur sensor ground for a sensor, use a power ground. Dont ground a sensor to chassis.
    Sensor grounds are just low noise grounds for low current inputs like pressure transducers and potentiometers that may be susceptible to noise from rotating electrical loads like fuel pumps, alternators, fans, etc.

    They're connected internally through a filter.

  17. #17
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    It's starting to make sense I think. Looking at my Bentley manual's Engine Management section for the 95 525i, harness-side pin 44 is title "SENS GRD" and leads to the IAT, Coolant temp sensor, and TPS. This pin seems like one that will need to be connected to White connector pin 18 "Sensor Ground" to reduce noise. I also received my 3bar MAP sensor which will need a ground. Shouldn't this also be ground with the other sensors so that noise isn't introduced or can other things be ground normally without the "Sensor Ground" pin of the MS3Pro?

    Ultimately, my question is: to achieve the proper grounding for the proper components, will multiple pins off the harness need to be connected to the "Sensor Ground" pin 18 of the MS3 or will each MS3 pin have its own individual pin on the harness?

    Thanks a ton for helping me out.

  18. #18
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    In general all the engine sensors will ground with the sensor ground pin or pins. You will likely need to splice multiple sensor grounds together which is not uncommon.

    I documented everything you'll need to do but for an aem controller. Download the chrome photobucket link fixer and take a look at my build thread.

    https://www.bimmerforums.com/forum/s...3#post28999373
    Last edited by Kevin325i; 05-31-2018 at 08:25 PM.

  19. #19
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    Quote Originally Posted by Kevin325i View Post
    Sensor grounds are just low noise grounds for low current inputs like pressure transducers and potentiometers that may be susceptible to noise from rotating electrical loads like fuel pumps, alternators, fans, etc.

    They're connected internally through a filter.
    Great explanation!
    -Nick
    91 E30 M42 on VEMS

    Turbo Camshaft Thread

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