Member
A few months ago January -ish, I bought a 2000 528i. I got a deal and it was low mileage. I was told by a mechanic selling it for a client, it had a bad throttle body(supposedly was throwing codes) but that for some reason they were selling as is--not interested in doing work --he did not appear to work on bmw. I bought car, it had symptoms relating to mdk (entering eml etc). So I bought a new (used ) throttle body, configured an old pc to run inpa, and did the install without diagnosing first. I ran adaptations etc, car ran fine for several months.
recently, the water pump catastrophically failed (bearings bound up). I replaced the pump. did the whole bleed and refill all that,. Car is back up and running not over heating. Since I had car apart anyway, I replaced some old boots on the air intake that were no longer supple had cracks (that were taped by previous owner.) But now the car is doing same thing again with the eml. It is throwing mdk plausibility errors and some lambda bank errors.
so I am re thinking the throttle body being bad as it seems somewhat unlikely to have two failed throttle bodies (though admittedly the one I installed is used) the TSB for my error codes says check the wiring using a break out box. I dont have one nor do I have the skills or time to build one. Anyone have some quick advice? is it possible to test the wiring minus a breakout box?
I have seen some suggestions to simply buy a new throttle body or a new wiring harness but prefer not to throw money and time and guess at problem. MAybe I need to go to the stealer. Any good tech living in ne Florida?
I would list the exact error codes, but I did not write them down, I tried to print the screen but now can't open the files they are in. If I get that sorted out ill list the actual codes.
the problem Is intermittent. I have driven the car perfectly fine for 10 mile trips but frequently in start up, it goes straight in to eml mode. has a rough idle and then throws mdk plausibility codes.
Member
I wish I could find a good article on use of inpa, because I’m not sure I’m doing this correctly.
So if I’m sitting in the car engine running with the car connected to inpa. If I clear the codes, the check engine light goes off. The elm light stays on . Then the service engine soon lights pops back on. And this code is thrown : 174 throttle flap poti.
My issue is the car keeps going in to eml. It’s spitting various throttle body codes. Throttle body was replaced 3 months ago with used part and ran fine for a few months. Beginning to suspect another issue.
Presently reading articles on possible brake light issue ( my brake light says the bulb is out but it’s not so pretty sure there’s a short in there somewhere ( perhaps that is throwing it into eml. Mode)
Planning on checking wire harness from mdk to dme per the tsb on mdk codes. But feel a little in over my head reading( or attempting to read ) the diagrams.
2000 528. Mtsu52 new
Sent from my iPhone using Tapatalk
Member
I recently went through a similar episode and ended up installing another used MDK. I have a thread on here somewhere about it. Be certain that you've re-connected your "new" MDK properly. That round connector is somewhat trixy. (Take a look in the following link, maybe the 7th or 8th photo down.)
https://www.newtis.info/tisv2/a/en/e...ration/BcsR8iI
The MDKs for these particular model-year 528i M52TU engines are a hybrid design that uses cable-actuation and DME control. Inside them the only parts that can fail are the two potentiometers. If you install a used unit, it probably will not be long-lived, considering how old it is. I went from a "yellow label" version to one with a blue label, which is claimed to have a revised design or component.... It was very tough getting the round connector to rotate all the way back onto the replacement MDK.
Originally Posted by bjornk
Member
Thank you! I actually read that article prior to install a while back and it was very helpful. It was tricky to get that Harness coupled...
I also went from yellow to blue. I don’t mind biting the bullet on a new throttle body, I just want to be 100% certain that’s the culprit.
I’m kind of wondering if my procedure of reading is correct. Meaning: if something else is throwing it into eml, mode. Could inpa simply be reading the condition of it being in eml?
Sent from my iPhone using Tapatalk
Member
Is your car a manual-shift or automatic trans? I'm not certain of all the things that can cause engine failsafe mode but on these M52TU engines a failing MDK very commonly causes that. If you saw my thread, you'll have seen the pics showing the potentiometers inside.
I did spray contact cleaner inside the two pots (well, through a couple of small openings) in the hope the circular tracks and brushes would be cleaned well enough to operate without faults for some time, if I ever have to re-install.
I think I'd prefer to just install a new one, though, having been through this once and knowing how old these things are now.
[Forgot to ask...] Did you clear throttle-body adaptations with INPA and do the "ignition-key-on, WOT four times, then turn-off-key" procedure when you installed the used one?
****
As to your brake light, did you confirm that the "third" brake light mounted at the center bottom of the rear windshield is also working?
You might want to double-check the type of bulb as well. Some have brass bases but I think I read that these cars prefer the ones with the non-brass base (nickel or steel?). Other thing to check would be the wiring harness connector plug on each bulb assembly, as the one on the right corner is known to corrode from exposure to acidic battery gases.
Last edited by pleiades; 05-13-2018 at 04:38 PM.
Member
codes bein thrown
174 throttle flap potentimeter. This code is thrown like clock work at idle when eml is on. Clear it and it shows again.
171 plausability error
169 mdk output stage comtrol after diagnostic
Member
MAnual transmission.
I did the inpa clear at install a coupe of months ago and had no issues until my water pump failed( i started another thread on this but didnt think it posted) , I did disconnect the air intakes and but on new boots. but i didnt touch the throttle body really, Maybe i need to get in there and see if i damaged a wire but doubt it.
I know my brake light has some kind of short. It says i have a bulb out. It was the third /center bulb which was indeed out. BUt since being replaced, it still sometimes sets off the bad light warning when driving along with an audible ding. But the bulb is fine. Yes, i was just reading these prefer a different bulb than the guy gacve me at my parts place...
- - - Updated - - -
Im with you though.. i think id rather replace the whole thing than play around cleaning and doing job repeatedly. I drive a lot...need it to work.
Member
If you haven't yet, it's quite easy just to check continuity over the harness between that round connector and the DME.
See this post.
And here's the diagram from the TIS.
Member
currently watching you tube videos on reading of automotive wiring diagrams. Voltage testers not my strong point. Are you saying just check each pin and trace it back to dme? guessing it goes through a few splices or harnesses. I found a diagram....
Probably need to do same thing on brake light..
Member
Just to add on to the thread. But on the TSB it states to replace engine wiring harness with updated harness. Is it possible the old harness can be causing a short due to its "bad" design and it is causing electrical issues with the car? How would you even test for a faulty engine harness?
I have been curious myself about threads in this forum about weird electrical problems that these cars may face. Could it be due to a faulty engine harness causing a bunch of issues? Maybe it is causing your "new" throttle body to act up?
Member
I scanned the above posts...where is the TSB? I wouldn't mind getting the part # of the updated harness.
I have a '99 528i 5-speed (125k miles) and I have been through 4 used throttle bodies (MDK) in the last 2 years. I have done all the replacements myself, and I pre-load the round elec MDK connector and reset adaptations with INPA / throttle depressions each time. The first 1-2 I thought I had bought a bad used MDK. the last few I removed personally from running parts cars, yellow or blue label, it didn't matter. Each one worked for a few months to a year. I now think I have a bad connection in the MDK connector (part of the engine harness). I have purchased a used replacement harness and next time the MDK fails, I will swap it in. I will pull the intake and swap the heater pipes while I am it.
The MDK can itself fail, but as others have suggested, I would suggest the OP check continuity between the MDK connector and the DME per Pleides suggestion. Please keep us posted.
Last edited by effduration; 05-14-2018 at 12:24 PM.
Having No Trouble Here
BMW CCA Member
There are LOADS of 'use of INPA' threads out there... whether they are 'good'... well that's another story...
Sounds like youre doing it correctly tho'. If you're clearing those and it keeps coming back... well... its "a thing" indeed for that motor.
pleasetheladies nails it. Notorious PITA for the motor. Its more famous on E36 boards because they just have more of those engines.
Notice multiple votes here for "a used one will probably just crap out again soon..."
I got no dog in this fight, and limited M52TU experience, but I have helped w bunch of M54 and M62 DBW throttle body fixes and there's at least related principles involved, even though those are full-DBW instead of semi...
The DME is looking for precision resistance measurements from the 2 pots on the throttle body. It compares the two and if they aren't precisely in sync, and/or, in a general range of plausibility that it expects, it says "oh isht! mayday mayday!".
Because its' resistance measurements, they can easily be skewed&screwed by a little extra harness or connector resistance. Wire corrosion under the insulation, a partial break in a wire invisible under the loom so that only 1/2 the strands are conducting, etc. So yeah... I think harness is worth looking at. My buds M54 was a bundle of intermittent failsafe hassles for ages until he finally bit the bullet and did the harness (individual pin-measuring BTW all looked 'fine' which he probably did 100x... so... yeah, that sucks...)
However, if it really was harness-only, then you'd think that if you take a failed-TB, refit it and fiddle w/ the wires and connectors, it would start working again for as long as another junkyard TB tends to work. The fact that this doesn't seem to be the case, and that a 'good used' TB will go in and work for a time, seems to indicate the throttle body pots ALSO wear and get contaminated and fall out of spec.
Engineering wise, it does seem like it is hyper sensitive. Obviously tha'ts because it's afraid of the throttle being stuck open and sending the car through a wall or a crowd of pedestrians, Toyota style. Now, for the DBW at least, I"ve come to believe this was poorly engineered and overly paranoid, since, the plausibility/error parameters seem to be excessively tight, and, you'd think that with the ability to monitor RPM and roadspeed and requested load (gas pedal independent of TB)... and the ability to kill ignition and fuel instantly.... Well if the engine RPM is increasing while 'requested load' is zero (i.e. no foot on the gas pedal), only THEN throw your FAILSAFE hissy fit. But that's a different story. In the case of the M52TU, it only measures the plate, not the pedal-too, so maybe it does have to be a bit paranoid about whether you're asking for throttle and getting throttle or not.
I'm not sure any of that is helpful whatsoever. Ha. But good luck anyway.
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)
Having No Trouble Here
BMW CCA Member
You have started 2 threads for the same problem.
Ask a mod to merge the 2 threads. (Done)
You're getting good help in the other one anyway.
Last edited by JimLev; 05-14-2018 at 09:25 AM. Reason: Threads were merged
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)
Member
What TSB are you referring to?
I'd believe this if you can show me a part number for an "updated" harness for the M52TU in the 1999 and 2000 model year e39 528i cars. Realoem only lists one P/N, and it does not supersede anything....
[edit] I found this, but it seems to be for the harness on cars equipped with auto trans...
12517503792
Does that one even plug into the TB?
Last edited by pleiades; 05-14-2018 at 12:32 PM.
Member
will do. I'll post the tsb when i get home its on the desktp. But it just says check harness if its not the harness repalce the mdk. pretty straightforward.
Harness is cheaper than the throttle body... I saw a board they use to test harnesses on you tube... way beyond my level of eletrical aptitude. I mean, a lot of the insulation is obviously weak/old/deteriorated. If the plan is to keep the vehicle, seems like a new harness could save a lot of time and money in the long run..Id want one with a recent manufacture date, not one thats been sitting on a shelf 18 years....
like gg stated, if its elctronic parts that are highly susceptible to minor changes in resistance... i can imagine the possibility of gremlins ... Ill keep this updated.
Member
I don't think it does. It looks to me like the "Periphery" harness plugs into the (auto) trans and may include the O2 sensors. The round plug you see appears to go into the Auto trans. If I want a new harness for my '99 528i manual, I believe I would need a complete new engine harness - part# 12511439175, and it prices out at more than $500...Ouch
Member
Yes, and that's the one that was never updated or superseded, with production probably halted at end of 2000, so about the best we can do is fork over $$$ for the "new" old inventory. Not terrible, I mean, my harness has been going almost 20 years, but I'm still curious about bd92's comment as it seemed to suggest we might have a choice of an "improved" version. Oh well ... my car is running great today .... the used blue-label MDK has yet to fuss.
Member
Thanks, im about to jump into those diagrams and check for continuity and resistance though I've heard from multiple people the resistance variance needed to throw the thing off may be minimal: maybe ill get lucky and see a huge problem. I would love to know what a break out box at the shop does. I imagine it puts a load on the lines and has more sensitive devices than a multi tester to detect strays.
so im not sure I have a "tsb" but i'll try to attach what I was looking at. Basically it looks like a tutorial from shop tools like snap diagnostics or maybe a Siemans manual. Oddly it doesn't list fault code 174 which is the code that keeps reliably popping up.
Last edited by bjornk; 05-14-2018 at 09:46 PM.
Member
I dont know why I said manual meant auto.duh...
Member
to be clear, the tsb does not say updated harness it just says replace harness..
Member
so im poking around and generally id say I know enough about electricity to cause some damage....and thats it.
Im a bit confused. by the DME pin numbering system. I started with the mdk to dme pin supplied by pleiades.. and stopped at pin one. Because on my dime, there is no cable at pin 4: its empty?
Im not 100% clear on what I would be looking for to test the harness or even to be honest how to test it. Im guessing I'll look for continuity , resistance, and possible short to ground -though the latter seems unlikely as the car is technically running.
as a point of reference- possibly for others--and for anyone who may be bored and want to explain to me what I am looking at or explain to me my lack of electrical foundations , I am measuring from the mdk connection with all wires still connected (hopefully I dint just blow up my dme--negative cable is disconnected) at 20k ohm. One probe to alternator, other probe to mdk pins....
pin 1 3.78
pin 2 13.79
pin3 12.82
pin 4 0
pin 5 12.83
pin 6 12.91
pin 7 0
pin 8 12.81
pin 9 13.6
pin 10 13.6
I realize this may be short to ground test which is most unlikely.
presently looking for a dme pin diagram.. though yes I can read the PIN numbers in the dme itself with a flashlight and magnifying glass. But why no cable on pin 4? maybe we have diff dme. I think I have ms42 engine system for ms52tu motor??
Last edited by bjornk; 05-15-2018 at 08:07 AM.
Having No Trouble Here
BMW CCA Member
babybjornbjork:
Here's a better assplinashun of the pinouts. Each sub-connector has a different number ("X60000whatever") and starts the pin-numbering over again.
http://www.bmw-planet.net/diagrams/r...39_PA6000E.htm
Test stuff independently first is one key...
So to test the harness, don't measure with it connected. There's way too much unknown and unpredictable to have any idea what the measurements are with the devices connected... you might even get a 'seems right' measurement vs a 'good car' but in fact the result is sorta-correct for the wrong reason...
Test the wires alone with nothing connected because we are SURE we know what those should be.
Same with testing the MDK itself, you'd want to do it without the wires on it to eliminate any cross-contamination of measurements, keep everything independent for testing first.
I would do this:
1. unplug both sides, and measure straight continuity resistance (from the MDK connector to where it comes out at the DME) on all 10 wires. You want all these to be effectively "zero ohms".
2. then, keeping it unplugged on both sides, yes I'd measure resistance to ground (to check for ground-shorts inside the harness someplace) on all 10. Here we want "infinite ohms".
3. then to get really gnarly, you measure resistance in between the individual wires... so..
Wire 1 -> wire 2, wire 1-> wire 3, 1->4, etc. to wire 1 -> wire 10
Move on to Wire2, but so as not to waste time measuring the same combo twice, when you move to pin 2 you can drop pin 1...
Wire 2 -> wire 3, wire 2 -> wire 4, etc.
Wire 3 -> wire 4, wire 3 -> wire 5 etc.
By the time you get to Wire 9 it should be just Wire 9 -> Wire 10.
All these ideally are infinite-ohms too, indicating no wires have any partial cross-shorts.
The "wired up" tests would be different, then you'd be measuring for the correct full-supply voltage and ground (zero voltage, zero ohms) on certain pins, and for certain 'plausible voltage' signals on other pins. Without digging deeper into the MS42 MDK wiring, I'm not sure what those would be... I'm guessing the MDK pots take a 5V supply signal and return that scaled to throttle-position...
But I'd try the disconnected tests first.
- - - Updated - - -
(BTW - the MDK harness is really TEN wires? that seems excessive!)
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)
Member
thanks GG,
That diagram works- I've added it to my files... I was looking at some other diagrams on another forum where they were looking at engine swaps and they apparently referenced other modules .
In hindsight, the numbers provided by pleiades can clearly only come from that module and were on the money.
I rigged a makeshift micro probe: those pins are tiny. So I have continuity on all pins...
dunno. I was leaning toward throttle body anyway...simply because this car seems pretty cherry and appears to be garage kept. While the gasket to the dme cover is shot..I swear the wires almost feel like they are still lubed. I really don't have any other electrical issues to speak of except for brake light. Pretty much everything else on the car works which seems a testament for an 18 year old car...
Im probably guessing there is a way using a breakout box to isolate those potentiometers and do further testing.... but seems like the throttle body is a known issue and bound to need replacing.....the $100 ebay part worked great for 3 months.
I saw on another post to attempt scrubbing pots at full throttle. I assume that means engine running and just for a sec..
Ive been going somewhat easy on this thing as I've not been certain of condition of hoses /belts etc. getting more familiar with the beast.
Member
Did you see Pleiades earlier thread on MDK replacement, with supporting comments from GG and others, re spraying a particular elec contact cleaner ( edit: Deoxit ) on the MDK pots as best you can? I liked how the best place to find this stuff is at a Guitar Center.
Last edited by effduration; 05-15-2018 at 08:02 PM.
Member
Yes! Saw that. I’ve been against the idea just because it seems a pita, and I might break something. I’d almost just get a new throttle body if it means avoiding random unexpected hours in shop tows etc .
However , gotta say I’m getting faster at taking this thing apart and putting it back together so... maybe it makes sense. 2-3 hours vs 500$ not a horrible hourly wage depending on the frequency . I kept the old throttle body —- May play with it.
For the record , I did read back through about scrubbing the pots . So I played with the throttle plate and did the WOT thing. I don’t fully understand that because I thought being electronic, there are fewer moving parts but... seems to work.. car ran like a top ..
Anyway this is a busy week for me and I have a loaner I promised to replace a steering pump in... so I’m going to put throttle body nonsense ioff and collect some hoses, gaskets , chase down that brake light short and if I’m going back in there again, I’m gonna get some maintenance things while I’m in there.
Sent from my iPhone using Tapatalk
Posting Permissions
Reply With Quote
Bookmarks