Page 2 of 2 FirstFirst 12
Results 26 to 49 of 49

Thread: Mdk! Wiring harness

  1. #26
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
    Join Date
    Mar 2010
    Location
    AndoverRockport MA & Intl
    Posts
    14,856
    My Cars
    E46M3Cic E39.540iT E84X1
    Two different things.

    Bridging OBD pins is about making sure you can see modules at both pin 7&8 on the OBD. That's mostly concern for later OBD only cars. Most purchased cables these days are already bridged there already but it's easy to check and see w multimeter.

    Bridging at the round connector means you take the pin w the "other modules" at the round connector, and bridge it over to the DME pin in the round which in turn is already sent to the OBD. Therefore sending all modules to the OBD.

    And your DMM is not autoranging (duh) if it has ranges. If it was autoranging it would only have "ohms" not 2M, 2k, 200, etc. ranges for ohms (and same for volts and everything else).

    Your testing prob is flawed - trying to test the listed resistance to chassis ground. You need to test to the appropriate pin pairs. I just looked up wiring on an E46 MDK. In this pic, 3 & 5 go to 4, 6 & 8 to 7... That's w wire / DME disconnected as you mentioned.

    https://forum.e46fanatics.com/attach...1&d=1450575326
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

    1985 MB Euro graymarket 300SL
    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  2. #27
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Quote Originally Posted by geargrinder View Post
    Two different things.

    Bridging OBD pins is about making sure you can see modules at both pin 7&8 on the OBD. That's mostly concern for later OBD only cars. Most purchased cables these days are already bridged there already but it's easy to check and see w multimeter.

    Bridging at the round connector means you take the pin w the "other modules" at the round connector, and bridge it over to the DME pin in the round which in turn is already sent to the OBD. Therefore sending all modules to the OBD.

    And your DMM is not autoranging (duh) if it has ranges. If it was autoranging it would only have "ohms" not 2M, 2k, 200, etc. ranges for ohms (and same for volts and everything else).

    Your testing prob is flawed - trying to test the listed resistance to chassis ground. You need to test to the appropriate pin pairs. I just looked up wiring on an E46 MDK. In this pic, 3 & 5 go to 4, 6 & 8 to 7... That's w wire / DME disconnected as you mentioned.

    https://forum.e46fanatics.com/attach...1&d=1450575326
    Thanks. I appreciate all the help I’m getting in this site . Both from direct comments and reading old discussions

    Im a little electrically retarded but trying to learn . I’ve been looking at that diagram for days.. looking up din symbols etc.

    This is what I’m thinking but not sure if it’s correct. So pins 3,5,4 represent the first double potentiometer which is basically a variable resistor and 6;7;8 are the other . Then there’s the motor that operates the plate, So the dme is symbolically on both sides of the mdk because it is watching to get driver wish and all that, but they clearly have to travel back and forth on the same set of wires I’m unclear of the connectors labled 31 in the dme. Is that the path to ground? It has a little symbol on one leg but it doesn’t look like the typical ground symbol .

    I’m not trying to test the mdk, pin pairs, I’m assuming it’s good as it’s brand freaking new . I’m trying to test for short to ground back through the wires to the dme: test the integrity of the harness/ connectors , are you saying I should be testing the wires in pairs? I’ve ranged through all the ranges — highest to lowest and still get infinite ohms on shirt to ground ( one lead to ground one lead to wire) I’m taking this to say the wiring is good. I suppose I could do some kind of voltage drop test too? I’ve tested continuity on the wire to the dme and it was good. I’m not sure I tested resistance, or whether that would show anything, in theory, with the dme disconnected shouldn’t the resistance of the wires from terminal to terminal be about the same? At least for 3 and 4, 5 And 6 and 7 and 8? : the pairs that go back to the same spot on the dme. Would a high — different from the others —-resistance show a short ?

    Pleiades and others have listed pot resistance on other posts but everyone acknowledges a manufacturer difference so I haven’t even tested for this on this Mdk. I’m assuming it’s good as it’s brand new,

    I found this site talking about testing voltage drop on the connector under the dash as a wiring harness test . Maybe I’ll try it but it seems like if you aren’t careful you could quickly fry a dme, Jimlev was saying that even after extensive testing , the wiring showed no issues but the mdk worked after the wiring was replaced, I thought there would be a way through testing to be certain a wiring harness is bad,

    So in theory the test below is saying if you know what circuit you are testing , you can see the voltage drop on that circuit? I guess once identified, you would back pin the connector on the dme with ignition on? That would /should have me feeling a bit nervous / shaky no?


    http://www.automotivetroubleshooting...ness_test.html

    You mentioned I may need a new battery because it was low when on. If the alternator is producing current, and giving 14 volts during charge, is the battery still coming in to play while running the dme?

    I’m feeling like I flipped a coin, heads is mdk tails wiring, I picked wrong, and now I need to do the harness two yeah!!! But what if it’s not the harness either,,,,,, I mean I have this thing so disconnected a new harness would be easy at this point I’m half way there,


    Sent from my iPad using Tapatalk

  3. #28
    Join Date
    Jun 2013
    Location
    Boston, MA
    Posts
    1,154
    My Cars
    99 528i/5, 05 ZHP conv
    BJornk keep at it.. You are likely to expand our knowledge of the mysterious M52TU MDK fails. How easy would it be to plug a separate MDK-only harness in? I am pretty sure the e39 6cyl auto trans harness (which I no longer need) has the same round 10-pin connector used on the '99 -'00 MDK.. I am thinking of making a separate harness for the just the MDK. How many plugs are there on the DME end? I mean do all the wires coming from the MDK connect to the DME in one plug? Or are they part of a bigger plug, or are there several plugs. Theoretically, I could run a bypass harness for just the MDK, and reduce the need for an entire new engine harness.

  4. #29
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
    Join Date
    Mar 2010
    Location
    AndoverRockport MA & Intl
    Posts
    14,856
    My Cars
    E46M3Cic E39.540iT E84X1
    Sorry man, if it makes you feel better, these ARE kinda convoluted circuits to be learning for "electronics 101 how to read a schematic" lesson. REALLY not one you would choose to teach some basic automotive schematic / electrical reading!

    OK I get that you aren't trying to test the MDK now.. (no you're right I didn't get that last night) and that's fine... but since you're trying so hard to understand the diagram I'm going to explain the MDK in that diagram anyway..?

    I think it will help you make heads or tails of how these things work...

    First of all I should say, you should confirm that the E46 M52TU MDK diagram matches the E39. I'm reasonably sure it should... but... probably should check that. Any comments below are purely about that E46 MDK diagram...

    Quote Originally Posted by bjornk View Post
    This is what I’m thinking but not sure if it’s correct. So pins 3,5,4 represent the first double potentiometer which is basically a variable resistor and 6;7;8 are the other . Then there’s the motor that operates the plate, So the dme is symbolically on both sides of the mdk because it is watching to get driver wish and all that,
    Correct, more or less. The DME 1. measures where you put the gas pedal with a pot, then 2. it sets the throttle plate with the motor, then 3. checks to be sure the plate went to the spot that it wanted with another pot. And it 4. constantly does that twice with a duplicate circuit to be sure there's no errors, since this could be a drastic safety problem (See toyota gas pedal crashes).

    And you're correct on the pins but actually each side also includes the supply terminals so each 'side' is 2, 3, 4, 5 and 1, 6, 7, 8.

    Lets just take one 'double pot' since they are basically identical.


    • DME provides a supply of voltage on on pin 2. We see in the diagram that it goes to both of the pot tracks. We know its power because of the "15" at the DME source, which is a DIN code for switched power.
    • That voltage travels to both pot-tracks and out to pin 4. We can see that because when pin 4 gets back to the DME it goes to "31", which is DIN code for ground. It also shows a little resistor there before the ground, which is technically correct to help us understand that the circuit is a voltage divider but even if it wasn't there, most people would guess it was a voltage divider anyway. So this is the main ground return for that circuit. But because its a voltage divider, some of the voltage coming from pin 2 also goes to...
    • Pins 3 and 5. These are on the 'wipers' of the pots. The part that moves and travels from one end to the other. That's what the little crossy-arrow-thing indicates. Because there's power at one end of each pot, and ground at the other end of each pot, you can imagine that when the wiper is at one end, you should see least zero ohms resistance to the supply pin 2, and 'full pot value' resistance to the 'ground' pin 4.... And when its at the other end, you should see the zero ohms resistance to the 'ground' pin 4, and 'full pot value' to supply pin 2. And with wiper set perfectly in the middle (OK there's 'pot tapers' to be considered but assume a "linear taper pot"...) you would see 50% of the resistance to each pin..
    • Now here's the part that you can't just figure out from looking at this without some BMW experience. Both 'driver wish' aka throttle-pedal position, and, the actual throttle plate position are measured by checking the volts that come back from those 2 pots. Pin 3 looks to be 'drivers wish' (gas-pedal position), and pin 5 looks to be throttle plate position. How do I know that? Sadly only via experience...
    • Look at the signal names. Those are the "U_DKFW2" and "A_FWG2" etc. Those are names of the signals on each wire. You can see the output signals are something about "FWG2" and "DKG2"? Well I know throttle-body in German is Drosselklappen, and that frequently it is abbreviated as "DK" in german and so if you see anything electrical named "DK" or "EDK" (or "MDK"... get it?) its probably a throttle body. Then, I also know BMW calls throttle-pedal 'drivers wish' in English a lot, and that "driver" is "Fahrer", so very likely FW = drivers wish = pedal position.
    • So the way the MDK works is to (1) measure your gas-pedal-cable position using pin 3, then (2) adjust the motor (using pins 9 & 10), then (3) check it using pin 5 to confirm that it is where it is supposed to be. And it does that twice - (4) using the mirrored circuit on 1/6/7/8, and is constantly comparing the two sides. If the 2 pedal-position ("FW") signals don't match, or the 2 throttle-plate ("DK") signals don't match, the DME thinks something is wrong w/ the MDK and goes into limp and throws errors.


    So - another disclaimer - I'm not an MDK expert, have only looked and and held them not actually tested one... And I hear that you have a new one so you aren't trying to test yours...
    But seems to me, to test an MDK you'd probably be looking to see that both 'sides' match up...

    FW pots:

    • Resistance measurements 2->3 (resistance from wiper-to-power-side) matches 1->6 at a few different gas-pedal settings
    • Resistance measurements 4->3 (resistance from wiper-to-ground-side) matches 7->6 at a few different gas-pedal settings


    DK pots:

    • Resistance measurements 2->5 matches 1->8 at a few different throttle plate movements
    • Resistance measurements 4->5 matches 7->8 at a few different throttle plate movements


    I don't know of that's what the other MDK experts here have tested - I'm sure they'll ring in - but I've seen at least a couple posts - including that E46 thread - that are measuring some weird stuff and I think not the right pin pairs -at least according to those diagrams...

    BTW here's the DIN circuit numbers - the most important of these are helpful to remember... which frankly are pretty much are mainly just 15 / 30 / 31... But standard relay terminals are helpful too (the ones that are in the 80's...) although I always have to look those up again...
    https://en.wikipedia.org/wiki/DIN_72552

    Quote Originally Posted by bjornk View Post
    I’m trying to test for short to ground back through the wires to the dme: test the integrity of the harness/ connectors , are you saying I should be testing the wires in pairs? I’ve ranged through all the ranges — highest to lowest and still get infinite ohms on shirt to ground ( one lead to ground one lead to wire) I’m taking this to say the wiring is good. I suppose I could do some kind of voltage drop test too? I’ve tested continuity on the wire to the dme and it was good. I’m not sure I tested resistance, or whether that would show anything, in theory, with the dme disconnected shouldn’t the resistance of the wires from terminal to terminal be about the same? At least for 3 and 4, 5 And 6 and 7 and 8? : the pairs that go back to the same spot on the dme.
    Well its pretty annoyingly tedious, but yes you want to test resistance - as a much better test for continuity - of each and every single strand... to a variety of 'destinations'. Disconnect both sides. Starting at one end or the other, pick a pin and test...


    • End to end to its output. It really should be effectively zero. You tested for continuity but do resistance.
    • Then yes test short to chassis ground.... sounds like you did that... that should be infinite.
    • Then test resistance from that one wire to each of the others... again should be infinite...
    • Then start again with the next wire...


    Quote Originally Posted by bjornk View Post
    Would a high — different from the others —-resistance show a short ?
    If you have either zero, or, measurable resistance where it should be infinite, then its a short.

    If you have a infinite, or, a measurable resistance where it should be zero, then it means the wire is broken (aka an "open") or if not a complete open, an otherwise poor connection... maybe 3/4 of the strands are broken at some point in the wire so it passes a continuity test but can't really carry all the current it should...

    Quote Originally Posted by bjornk View Post
    Jimlev was saying that even after extensive testing , the wiring showed no issues but the mdk worked after the wiring was replaced, I thought there would be a way through testing to be certain a wiring harness is bad
    Yep. Absolutely. Jims talking about his M62TU harness but I've seen same thing w M54 harness - tests fine over and over but replace it and it all works. That probably means theres an intermittent short or open, or, maybe there's some other inductive interference between the wires or something. Basically if you had enough fancy electronic test gear you probably COULD prove why those cases are failing (shooting AC signals down the wire, testing inductance, testing current-capacity...), but a basic DMM just isn't quite enough.

    You could also test the various pins for voltage WITH the ignition on and MDK connected, but you need the proper reference values. You need to know what voltage is expected at pins 2, 3, 4, 5 etc. for a known good motor with the throttle cable at idle and then WOT position... I dunno if any of the 100's of MDK threads have listed that diag procedure...

    Ignore that webpage.
    Last edited by geargrinder; 10-03-2018 at 11:06 AM.
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

    1985 MB Euro graymarket 300SL
    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  5. #30
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Thanks fir the detailed explanation on the mdk. I’ll re read it a few times with the diagram in hand but most of that makes sense,

    I’ve got the thing apart so I’ll continue with the resistance tests etc and others , it would be great to get a definitive yes test before dropping 5 bills on a harness.

    Living in Florida, we have a ton of humidity and heat, gauging from that size of that wire and what is described as a sensitive tolerance on the coding of the potentiometer variables... I can imagine it doesn’t take much to throw those readings off: a little condensation and a little crack in the wire...

    I’ll keep at it,,,and keep ya posted,

    If anyone can think of any “ other” possibilities ( or rather likelihood’s ) for the eml when the dme /Inpa is only throwing throttle body codes let me know......


    Sent from my iPad using Tapatalk

  6. #31
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    Quote Originally Posted by effduration View Post
    BJornk keep at it.. You are likely to expand our knowledge of the mysterious M52TU MDK fails. How easy would it be to plug a separate MDK-only harness in? I am pretty sure the e39 6cyl auto trans harness (which I no longer need) has the same round 10-pin connector used on the '99 -'00 MDK.. I am thinking of making a separate harness for the just the MDK. How many plugs are there on the DME end? I mean do all the wires coming from the MDK connect to the DME in one plug? Or are they part of a bigger plug, or are there several plugs. Theoretically, I could run a bypass harness for just the MDK, and reduce the need for an entire new engine harness.
    The cheapskate in me is tempted to do the same. But I guess you’d have to buy a few specialty connectors, a few terminal ends, know exactly what gauge wire to get and be super confident in your crimping skil.s I kind of did the math and you’d probably spend 200... so you’d save 3.unless your crimps were bad etc, weaving everything in to that loom and to the backside of that dme pin connectors seems the worst part. And then if you were me, you’d wonder if you crimped that terminal just right or if you did it after a couple of cocktails.

    Every time I take those dme connectors off I hold my breath like I’m doing surgery or something, they look like the same plastic as the one under my drivers seat held together with gorilla tape and a strap tie,,,,don’t think that would fly in that box....maybe I should switch that connector out first as a practice exercise.... less at stake.

    On the positive side, I’ve got that harness pretty exposed at this point if I decide to pull it,,,,
    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-03-2018 at 06:03 PM.

  7. #32
    Join Date
    Jan 2015
    Location
    Shreveport Louisiana
    Posts
    762
    My Cars
    1999 5281
    shorting pins 17 and 20 on the pacman cap will enable you to read other modules than the trans and DME using the 16 pin OBDII connector.

  8. #33
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Well I did the accelerator cable, cleaned my iacv, and changed that ground. I have yet to reset anything or pull any codes (I will ) but the car is running great no eml no ses light. Forgot to get a new accelerator grommet and the old one broke so I’m driving gently...

    I would have liked to do one thing at a time to know definitely my cause but I don’t have the patience for that.

    The iacv was definitely stuck. It was in a slightly open position. It wasn’t rattling- could not be shook loose even when it came out of the Car. Compressed air and throttle body cleaner seems to have worked. now it’s free and you can hear it buzz though you really have to know what to listen for, the idle now is much better and the difference when I put the ac on is better: it might drop 100rpm...it used to drop like 2.. All these changes though are pretty subtle. I bought the car used and felt it ran okay. I maybe would have noticed had I been driving it daily prior to it acting up but it’s subtle . I defitely nitice better acceleration. The Bentley manual I had have the wrong resistance for testing, they listed an update that is more in line with the reading I got. I’m kind of thinking this was my issue.

    My ground measured fine on a ohm meter but looking at it, and the bolt that held it on definitely made it a bit suspect. Seems like something is going on.I’m surprised the zinc plated bolts are used going into what looks like aluminum framing: maybe it’s an alloy, anyway I git that that all dialectriced up...

    Gonna run it a few days or weeks and then pull codes. Think my next job will be trifecta. Bunch of handing sensor looking things that fall apart when you touch them...


    Sent from my iPad using Tapatalk

  9. #34
    geargrinder's Avatar
    geargrinder is offline Having No Trouble Here BMW CCA Member
    Join Date
    Mar 2010
    Location
    AndoverRockport MA & Intl
    Posts
    14,856
    My Cars
    E46M3Cic E39.540iT E84X1
    DUDE that ground cable is TERRIBLE! Holy guacamole & frijoles. That very well might be the cause of all kinds of weirdo symptoms.
    2003 M3CicM6 TiAg
    2002 540iT Sport Vortech S/C 6MT LSD TiAg
    2008 Audi A3 2.0T DSG (the daily beater)
    2014 BMW X1 xDrive28i (wifemobile)

    Former:

    1985 MB Euro graymarket 300SL
    1995.5 Audi S6 Avant (utility/winter billetturbobattlewagen)


  10. #35
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    In the on_going saga of the mdk, i am back to throwing codes.. jumping into eml. Albeit slightly different: unless someone
    interprets this differently ...I think I’ve avoided the harness job long enough.

    Car ran great 7 days. Even a few 50 mile trips.

    Here are some numbers to look at-
    My thoughts, and honestly I’ve no idea what normal looks like.1) my pwg voltage on pot one and two look pretty diff . Especially compared to the mdk pot 1 and 2 which is much closer. I wonder what the formula is on the adaption value, I think this is at 1500 rpm dkp Angle at 5 ish


    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-17-2018 at 10:14 PM.

  11. #36
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    I think I took this at idle and fir a sec, the diff between pwg pot 1 and 2 are close.




    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-18-2018 at 04:12 PM.

  12. #37
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness



    K ring at o . Think this is at idle too but note the drastic drop in voltage on pot 1.


    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-18-2018 at 04:14 PM.

  13. #38
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    I’ll post codes in am.thought I took pics .. I think there were two new codes but most were similar mdk plausibility errors. Hard jam etc...

    Is this bad etiquette posting pics?




    Sent from my iPad using Tapatalk

  14. #39
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    Ok so the codes are..and I can post pics if more info needed—- times frequency etc,
    119 mdk mechanical jam
    171 plausibility
    110 pot 1 signal ( feel like this is new)
    175 adaptation
    117 pwg pot 1/2
    8 air flow meters ( feel like this is new) volatage was at zero, I don’t know if that’s normal, I know that when I bought car, it had a new maf installed and the old maf was in the new maf box, which lead me to think maf was replaced but was no the issue,
    And finally 118 pot 1and 2 plausibility .

    So today on a quick run out, car ran fine, so I checked same screens and this time , my pots were much closer aligned as opposed to the pic I posted where they were considerably off, notice pot one in this pic is .77. In first pic while in eml. Pot was .39, Looks likes most the pots aren’t off by more that.05 generally often less. So in the first shot with car in eml, the pot is way off from its corresponding pot.




    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-18-2018 at 04:16 PM.

  15. #40
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Quote Originally Posted by bjornk View Post


    K ring at o . Think this is at idle too. Notice pwg pot 1 is way down around .2 volts. That’s seems suspect. My old pots ran closer to 4 at idle, the other 3 pots seems to be running closer to 1. .7,..8. You’d think all four pots would be kind of close, even if the computer can calculate a range diff. Also to see it fluctuate at idle from .2 to .7 doesn’t seem right nothing else is moving like that.

    It’s hard to catch the spike on the pots using inpa and hitting the throttle but generally you do see them move in sync. I feel like it’s that pot!!!

    Or I guess the voltage being supplied to it...


    Sent from my iPad using Tapatalk



    Sent from my iPad using Tapatalk

  16. #41
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    Gg wrote:[*]DME provides a supply of voltage on on pin 2. We see in the diagram that it goes to both of the pot tracks. We know its power because of the "15" at the DME source, which is a DIN code for switched power.[*]That voltage travels to both pot-tracks and out to pin 4. We can see that because when pin 4 gets back to the DME it goes to "31", which is DIN code for ground. It also shows a little resistor there before the ground, which is technically correct to help us understand that the circuit is a voltage divider but even if it wasn't there, most people would guess it was a voltage divider anyway. So this is the main ground return for that circuit. But because its a voltage divider, some of the voltage coming from pin 2 also goes to...[*]Pins 3 and 5.


    Doesnt it make sense then that the voltage on pots 1 and 2 should match and the fact that they don’t is my issue which is being captured in one pic..where you’d have a spread of nearly .5 which doesn’t appear to be the spread in any of the other pots. In addition, this super low voltage was captured while car is in EML. So the same pot is reading .77 when not in EML. So likely, there as short or open in that harness bringing the supply to the pot. Or is it pointing to a bad pot... fresh out the box— brand spanking new...


    Sent from my iPad using Tapatalk
    Last edited by bjornk; 10-18-2018 at 04:10 PM.

  17. #42
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto

    Mdk! Wiring harness

    Quote Originally Posted by geargrinder View Post
    Sorry man, if it makes you feel better, these ARE kinda convoluted circuits to be learning for "electronics 101 how to read a schematic" lesson. REALLY not one you would choose to teach some basic automotive schematic / electrical reading!

    OK I get that you aren't trying to test the MDK now.. (no you're right I didn't get that last night) and that's fine... but since you're trying so hard to understand the diagram I'm going to explain the MDK in that diagram anyway..?

    I think it will help you make heads or tails of how these things work...

    First of all I should say, you should confirm that the E46 M52TU MDK diagram matches the E39. I'm reasonably sure it should... but... probably should check that. Any comments below are purely about that E46 MDK diagram...



    Correct, more or less. The DME 1. measures where you put the gas pedal with a pot, then 2. it sets the throttle plate with the motor, then 3. checks to be sure the plate went to the spot that it wanted with another pot. And it 4. constantly does that twice with a duplicate circuit to be sure there's no errors, since this could be a drastic safety problem (See toyota gas pedal crashes).

    And you're correct on the pins but actually each side also includes the supply terminals so each 'side' is 2, 3, 4, 5 and 1, 6, 7, 8.

    Lets just take one 'double pot' since they are basically identical.


    • DME provides a supply of voltage on on pin 2. We see in the diagram that it goes to both of the pot tracks. We know its power because of the "15" at the DME source, which is a DIN code for switched power.
    • That voltage travels to both pot-tracks and out to pin 4. We can see that because when pin 4 gets back to the DME it goes to "31", which is DIN code for ground. It also shows a little resistor there before the ground, which is technically correct to help us understand that the circuit is a voltage divider but even if it wasn't there, most people would guess it was a voltage divider anyway. So this is the main ground return for that circuit. But because its a voltage divider, some of the voltage coming from pin 2 also goes to...
    • Pins 3 and 5. These are on the 'wipers' of the pots. The part that moves and travels from one end to the other. That's what the little crossy-arrow-thing indicates. Because there's power at one end of each pot, and ground at the other end of each pot, you can imagine that when the wiper is at one end, you should see least zero ohms resistance to the supply pin 2, and 'full pot value' resistance to the 'ground' pin 4.... And when its at the other end, you should see the zero ohms resistance to the 'ground' pin 4, and 'full pot value' to supply pin 2. And with wiper set perfectly in the middle (OK there's 'pot tapers' to be considered but assume a "linear taper pot"...) you would see 50% of the resistance to each pin..
    • Now here's the part that you can't just figure out from looking at this without some BMW experience. Both 'driver wish' aka throttle-pedal position, and, the actual throttle plate position are measured by checking the volts that come back from those 2 pots. Pin 3 looks to be 'drivers wish' (gas-pedal position), and pin 5 looks to be throttle plate position. How do I know that? Sadly only via experience...
    • Look at the signal names. Those are the "U_DKFW2" and "A_FWG2" etc. Those are names of the signals on each wire. You can see the output signals are something about "FWG2" and "DKG2"? Well I know throttle-body in German is Drosselklappen, and that frequently it is abbreviated as "DK" in german and so if you see anything electrical named "DK" or "EDK" (or "MDK"... get it?) its probably a throttle body. Then, I also know BMW calls throttle-pedal 'drivers wish' in English a lot, and that "driver" is "Fahrer", so very likely FW = drivers wish = pedal position.
    • So the way the MDK works is to (1) measure your gas-pedal-cable position using pin 3, then (2) adjust the motor (using pins 9 & 10), then (3) check it using pin 5 to confirm that it is where it is supposed to be. And it does that twice - (4) using the mirrored circuit on 1/6/7/8, and is constantly comparing the two sides. If the 2 pedal-position ("FW") signals don't match, or the 2 throttle-plate ("DK") signals don't match, the DME thinks something is wrong w/ the MDK and goes into limp and throws errors.


    So - another disclaimer - I'm not an MDK expert, have only looked and and held them not actually tested one... And I hear that you have a new one so you aren't trying to test yours...
    But seems to me, to test an MDK you'd probably be looking to see that both 'sides' match up...

    FW pots:

    • Resistance measurements 2->3 (resistance from wiper-to-power-side) matches 1->6 at a few different gas-pedal settings
    • Resistance measurements 4->3 (resistance from wiper-to-ground-side) matches 7->6 at a few different gas-pedal settings


    DK pots:

    • Resistance measurements 2->5 matches 1->8 at a few different throttle plate movements
    • Resistance measurements 4->5 matches 7->8 at a few different throttle plate movements


    I don't know of that's what the other MDK experts here have tested - I'm sure they'll ring in - but I've seen at least a couple posts - including that E46 thread - that are measuring some weird stuff and I think not the right pin pairs -at least according to those diagrams...

    BTW here's the DIN circuit numbers - the most important of these are helpful to remember... which frankly are pretty much are mainly just 15 / 30 / 31... But standard relay terminals are helpful too (the ones that are in the 80's...) although I always have to look those up again...
    https://en.wikipedia.org/wiki/DIN_72552



    Well its pretty annoyingly tedious, but yes you want to test resistance - as a much better test for continuity - of each and every single strand... to a variety of 'destinations'. Disconnect both sides. Starting at one end or the other, pick a pin and test...


    • End to end to its output. It really should be effectively zero. You tested for continuity but do resistance.
    • Then yes test short to chassis ground.... sounds like you did that... that should be infinite.
    • Then test resistance from that one wire to each of the others... again should be infinite...
    • Then start again with the next wire...




    If you have either zero, or, measurable resistance where it should be infinite, then its a short.

    If you have a infinite, or, a measurable resistance where it should be zero, then it means the wire is broken (aka an "open") or if not a complete open, an otherwise poor connection... maybe 3/4 of the strands are broken at some point in the wire so it passes a continuity test but can't really carry all the current it should...



    Yep. Absolutely. Jims talking about his M62TU harness but I've seen same thing w M54 harness - tests fine over and over but replace it and it all works. That probably means theres an intermittent short or open, or, maybe there's some other inductive interference between the wires or something. Basically if you had enough fancy electronic test gear you probably COULD prove why those cases are failing (shooting AC signals down the wire, testing inductance, testing current-capacity...), but a basic DMM just isn't quite enough.

    You could also test the various pins for voltage WITH the ignition on and MDK connected, but you need the proper reference values. You need to know what voltage is expected at pins 2, 3, 4, 5 etc. for a known good motor with the throttle cable at idle and then WOT position... I dunno if any of the 100's of MDK threads have listed that diag procedure...



    Ignore that webpage.
    If pin 3 is drivers wish, then You basically turn it, like a volume control when you step on the gas.. actually physically, you are turning the wiper via cable? Thus, if you have reset the throttle cable correctly, then with the car at idle, no foot on gas—-you would get zero resistance because the wiper In theory is close to zero: the spring puts it there, and it could read that fine, even if all the other wipers are stuck in the middle...it doesn’t matter what voltage they are spitting out, the final number goes through some ratio calculation. So the voltage at idle would possibly be lower than the other pots? I’m thinking they should be very close as they are all sharing a similar circuit. But maybe the wipers are in different positions?
    What is that voltage is my q? Is .20 an indication of a lack of voltage ? Can I guess that’s it’s a harness versus a pot issue?

    Depending on the locations of the wipers on the other pots, ( are they on springs and constantly returning to zero? Or are they electronically controlled by the dme based on reading by the other pots and coding logic? If it’s not actually zero thats okay, the dme isn’t actually going off that wiper anyway, it’s going off some calculations of the combined readings. Ultimately, all these number go through the dme, and the dme sends the voltage to the motor driven plate, in milliseconds—- crazy really,... So the voltage going in.. could it be as little as .20v. And still work? I mean isn’t the dme just creating number and logically keeping them within certain parameters plus minus some percentage ....

    So the real issue is the adaptation. You set an adaptation and it’s takes the input at idle at .70. Or 0 or ..05, or 3 or 4 But it’s suddenly fluctuates to .20.. then it’s fubar...because the computer thinks is should be at that original value.

    Or theoretically, it could even set that start point at zero,

    Seems like if it were that low, the throttle cable adjustment could be tricky af.

    Seems there should be a way to ask the computer what value it is working off of? Show the value it has loaded as a basis when you set adaptation. Pull up that file, look at the input ....

    I I’m looking at ohms law
    Last edited by bjornk; 10-18-2018 at 11:58 PM.

  18. #43
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto



    Sent from my iPad using Tapatalk

  19. #44
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Think im rolling the dice on the harness.

    My conclusions are based n the following:

    1) When im sitting at idle looking at pot 1, I now notice the voltage really fluctuates up and down even when nothing is touching the pedal. I have video. Im seeing the voltage range from .25 to .50 when the car is in eml: quickly and randomly and very out of sync with pot 2. and those numbers are far off from the other pots. When the car is running normal. the voltage is about .77 at idle and within about 5-10% of the other pot. IN addition, under normal circumstances, the voltage is stable. and fluctuates only with acceleration.

    I found this link on bimmerfest, I think it does a good job summarizing many issues mentioned here is a pretty simple write up kind of mdk for dummies...





    Originally Posted by IROLL24
    Thanks I'll test the resistance on those wires

    Let me give you step by step guide to test MDK.

    See my diagram below for the description of pins and also refer Shanneba's diagram to see how they are related.

    There are two sets of throttle position sensors in MS42's MDK.

    1. Test reference voltage:
    With key on,
    Multimeter setting: low voltage,
    - lead: chassis ground,
    + lead: pin 1 on DME side of connector X6385 (10 pin connector to MDK)
    Result: should lead 5 volt
    Next connect + lead to pin 2 on DME side of connector X6385 (10 pin connector to MDK)
    Result: should lead 5 volt
    2. Continuity test for all sensors (potentimeters)

    Remove the MDK from engine and do bench test.
    Multi-meter setting: Ohm measurement

    Check throttle sensor 1 continuity
    - lead: Pin 7 on MDK side of connector X6385
    + lead: connect to pin 1, 6, and 8 in sequence and make sure there is no open circuit in any of the connection.
    I have no reference value for the resistance, and you may need to adjust the range of multi-meter to measure them.

    Do same for throttle sensor 2
    - lead: Pin 4 on MDK side of connector X6385
    + lead: connect to pin 2, 3, and 5 in sequence and make sure there is no open circuit in any of the connection.
    3. Throttle position sensor 1 and sensor 2 match test with varying throttle openings

    Two multi-meters will make this test simpler, but you can get by with one by wedging varying thickness objects in the valve and body to change opening angle.
    Multi-meter setting: Ohm measurement

    At varying throttle angles including closed and wide open throttle, measure and record following resistances:

    A. pin 7 and 8
    B. pin 7 and 6
    C. pin 4 and 3
    D. pin 4 and 5

    If my guess is right, A and C should be very close and also B and D should match closely.
    [IMG][/IMG]

    __________________
    Code Search: https://docs.google.com/spreadsheet/...tZ05Dd2c#gid=0

    Part Number: http://realoem.com/bmw/select.do?kin...ies=E46&arch=0
    Last edited by bjornk; 10-23-2018 at 08:20 PM.

  20. #45
    Join Date
    Jun 2013
    Location
    Boston, MA
    Posts
    1,154
    My Cars
    99 528i/5, 05 ZHP conv
    Are you getting a new or used harness? If buying new (like $550?) remember the 20% CCA discount many dealers offer. Price shop the usual online sources.

  21. #46
    Join Date
    Feb 2018
    Location
    San Mateo, FL
    Posts
    127
    My Cars
    2000 E39. MS52TU, auto
    Quote Originally Posted by effduration View Post
    Are you getting a new or used harness? If buying new (like $550?) remember the 20% CCA discount many dealers offer. Price shop the usual online sources.
    I think I’ve seen for as low as 440. I have some stuff bookmarked. There’s a bmw dealer selling on amazon too guess Bezos has a way to twist everyone’s arm...I’ve looked at CCA but not a member yet


    Sent from my iPad using Tapatalk

  22. #47
    Join Date
    Jun 2010
    Location
    Bay Area, California
    Posts
    1,305
    My Cars
    325iT, 540iT
    You'd have to look up the BMW docs to make sure but I'd expect the two pots to be different (with each one running on a different scale to provide some sort of sanity checking). Crazy readings would make me think that the pot itself is bad (worn/dirty wiper, etc). Although, yeah, BMW isn't always great about weather sealing their wiring -- I grabbed a 20 pin connector off of a 750 the other day and when I cut into the sheath water just poured out. The wires were pretty well rotted, but good enough for my purposes.

  23. #48
    Join Date
    Jan 2022
    Location
    UK
    Posts
    1
    My Cars
    1999 BMW 323i E46
    Had similar error relating to the TB

    A9 or 169 in INPA (shut off after diagnostic) being caused by the following...
    p0120 or 172 in INPA ( short circuit )
    p0220 or 173 in INPA (short circuit )

    Obviously one of the 10 wires to the TB were open/shorting.

    Until I took the 54 pin plug for the TB loom out the ECU. The 54 pin socket was water logged and covered in green goo from the shorting out!!
    Other sockets were perfectly dry and clean?? Wicking or shorting has created this damp patch.
    Dried and cleaned it all up.
    Cleared codes with INP and reset adaptions.

    All sorted!!

    Sideways Sally again!

  24. #49
    Join Date
    Jun 2013
    Location
    Boston, MA
    Posts
    1,154
    My Cars
    99 528i/5, 05 ZHP conv
    I recently followed up with Bjornk because I was curious. He told me he still owns his E39 with the M52tu engine and that after he bought and installed a new engine wiring harness, he hasn't had a problem with the MDK...

    New OEM harnesses are getting hard to find... and if you do find one they are extremely expensive. Here is another option to replace just wires for the MDK.

    MDK Repair

Page 2 of 2 FirstFirst 12

Similar Threads

  1. Can't Find Wiring Harness
    By O=00=O 2002 in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 0
    Last Post: 04-19-2002, 05:38 PM
  2. WTB: E30 Ellipsoid Wiring Harness
    By satyen119 in forum BMW Parts Wanted
    Replies: 0
    Last Post: 02-07-2002, 11:53 AM
  3. Wiring harness to hook aftermarket head to factory HK speakers/amp?
    By IK632 in forum Car Audio & Electronics sponsored by Bavsound
    Replies: 1
    Last Post: 01-25-2002, 11:06 PM
  4. Question about wiring harness......
    By Mike88 in forum Car Audio & Electronics sponsored by Bavsound
    Replies: 2
    Last Post: 01-18-2002, 08:45 AM
  5. Replies: 0
    Last Post: 08-02-2001, 06:53 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •