Not possible to swap just the TB, because the DME, wiring, etc., all expect that type.
You would have to also swap to a matching DME, such as MS43, which is a much bigger project.

Have you read through all the existing M52TU TB threads on here? There are many.

Search results for query: M52TU throttle

www.e46fanatics.com

 

Been there and done that.

It is not likely you have another bad TB. What is likely is that there is corrosion, etc in the stupid round 10-pin connector which points toward the rear of the car and which has no rubber to protect the connections from the elements and the air stream around the engine...

As you may know the Throttle body /DME in the M52TU engine is extremely sensitive to changes in resistance, voltages, etc. A deterioration in the wiring is likely a cause of your issues.

you have a couple of options.
1. Spray de-oxit or something similar in the back of the connector - might or might not work
2. Replace with a used M52tu harness - might last for a while
3. Replace with a new harness - part# avail on RealOEM. Expensive and likely not avail.
4. Replace just the connector as outlined here:

Electronic Throttle Faults & Repair

Diagnosing electronic throttle body faults and replacing its connector plug on 99-00 BMW 5 series.

www.frankies-bmw.com

There are people who have tried - with mixed success - to wire in an M54 Drive by wire pedal. Usually done as part of an upgrade from M52TU to M54. Not easy, and full of risk of add'l problems - Not recommended.

323Ci (M52tuB25) to M54B30 Complete Conversion, with...

As I mentioned in my header build thread, http://forum.e46fanatics.com/showthread.php?t=829844&highlight= a buddy of mine was DD'ing. Long story short, I egged him on to drive the car hard and he money-shifted it. Based on gear ratios and engine speed when he shifted, I calculated 8500 RPM. I...

www.e46fanatics.com

 

i had to get a used TB and couple months pass by and now this one is done, getting constant EML and limp mode from throttle issues

Most of the time this issue was caused by the TB butterfly valve seized and doesn't move freely. Clean up the TB barrel around the valve should fix it.

 

OP has already replaced his TB once...So were both butterfly valves seized?
It's fine to clean the throttle body, I just wouldn't manually open and close the main vane. Treat it gingerly.

 

I'd remove the tb and icv, clean both well with tb cleaner, replace gaskets, lube throttle cable...and make sure the icv connection is on right. It's a pitb two-stage connector that will make you think it's on okay, when it's not.

Turn icv every direction you can and spray then drain fluid until you hear the valve brightly clicking.

 

Any updates @e46lucas ? I am having the same issue for a long time, tried changing TB (used) 3 times. Same issues. The only thing that was changing is how fast it went to limp mode at first I drove for couple of months then weeks, now it fails within 20 minutes...
Thanks @Effduration for the tips I should probably try the 4th tip (Replace just the connector). Just don't want to ruin something which I am not sure is the problem.
Attaching the pics of error codes in INPA I am having in random order:

 

I actually disconnected the connector and sprayed some electrical connector cleaner thing from autozoneon both sides of the connector like the side you plug into the throttle body and the side where the wires go into the connector, let it dry and sprayed it again, and when it was dry I plugged it back in and it worked fine ever since

 

A clue from the 112 code. Potentiometer 1 does not have a power supply. It should be 5V. You need to check the voltage at pins 2 to 4 and 1 to 7 at the MDK or there equivalent at the DME end.

Attached is some MDK information I have found on the Interweb over the years. Hope it is useful.

 

Thanks a lot! That PDF is a gem. First will test the TB then will do the voodoo on the 10-pin connector. Meanwhile found 2 more photos of other error codes from past.
It's annoying how one error code (173) says "short circuit" other (119 from earlier post) says "mecanical error" :-|

 

I've tested one of my "failed" TBs (other one is under the hood yet). There are clear deviations from the PDF provided by @NZ00Z3

Requirements: 1600 - 1000 Ohm, tolerance: 10%
2 & 5 : 1866 - 1228
2 & 3 : 1720 - 977
1 & 6 : 1753 - 1012
1 & 8 : 1843 - 1182

Requirements: 1000 - 1650 Ohm, tolerance: 10%
4 & 3 : 1035 - 1725
4 & 5 : 1040 - 1725
7 & 6 : 1066 - 1758
7 & 8 : 1205 - 1848

I am a complete newbie so I'd appreciate any advice. Are the above measurements enough evidence to be sure that TB is broken?

 

What are the readings for pins?

• 2 - 4
• 1 - 7

Its a resistance divider circuit, so need the above reading as the starting values.

The information was found on the Interweb some time back. It's likely the readings some owner got when testing a MDK. I would not yet use the numbers as a hard and fast pass/fail test until we get some experience with them. Get me the above requested values and I run them through a spreadsheet for you.

 

2 & 4 : 982
1 & 7 : 992

 

BMW (and many other manufacturers) strongly advise the use of "Stabilant 22" for applying to the connector pins, both male and female for such instances. It's fooking expensive, but if there's a connection issue with the pins and varying resistance is the root, the Stabilant usually fixes it.

FYI.

 

Thanks for this...It sounds a little like a commercial/professional grade De-Oxit. The first google search result on Stabilant 22 came from Boeing....

I think I am going to try it before I either replace harness (with another used harness) or replace pins as suggested above...

Here is a description of Stabilant 22: '

Posthorn | Stabilant 22

"...Its advantage lies not in making new contacts better, but in keeping contacts operating as if they were new, while making old contacts function perfectly despite the ravages of time and adverse environments...."

 

Alternative input from another M52Tu user

Could it be the cause of the EML is the throttle cable itself and not the pin connectors? I’m using an M56 intake manifold (same port size as M54B30) with a Turner adaptor plate mated to an M52Tu throttle body. The manifold is not meant
to be used with the M52Tu TB, more so with a spacer, so TB cable does not sit at
the default location.

I had a couple of events where the TB cable orientation or tension was incorrect on the mount and caused an EML/Limp mode, limited to 50-55 mph.
I don’t remember the exact code, since I was on the road at the time, but had to reach in and slip the cable in such a way it didn’t bind or the cable tension is at an acceptable range. I think there was interference with the bracket that held the sucking jet pump for the brake booster and the code was TB potentiometer error.

This was btw on post Manual 5-Speed swap indicating throttle, even with a cable actuation, is electrically controlled/limited. Much like late 90’s Mercedes but the potentiometer is separate from the TB.

I haven’t had the problem since and switching to Ms43 soon just to simplify the car more.


Sent from my iPad using E46Fanatics

 

I've had a good look at the test results.

The design of the MDK is interesting.

• There are 2 sets of Potentiometers. This allows the DME to compare one with the other to create a fail-safe system.
• Within each set, one potentiometer is biased the opposite to the other. This allows for mathematical checks within the potentiometer set. More fail-safe features.
• All connections within the potentiometer sets are available to the DME. This allows for mathematical checks between the potentiometer set. Yet more fail-safe features.
• The potentiometers within a set are connected in parallel. From the test results we can conclude that the individual potentiometers have the same resistance, that is twice the resistance of the paralleled pair, so that is 2,000 ohms.
• The test results show that the minimum resistance on each potentiometer is 1,000 ohms.
• This makes sense. Engineers like using easy numbers, so a 2,000 ohm Potentiometer with a 1,000 ohm minimum reading, gives a 1,000 ohm range for 100% travel, or 10 ohms per every 1% of travel.
• The potentiometer supply is 5V. This means that the maximum current draw is 5/1,000 = 5mA and the minimum current draw is 5/2,000 = 2.5mA on any leg of the system.
• We test for resistance but the DME measures Voltage.

What we do not know, is what mathematical checks the DME does to ensure that the MDK is safe to use. There are a lot of options with the layers of fail safe in the design.

We do know that the MDK has problems with poor electrical connections. The added resistance upsetting the checks and balances (fail-safe) that the DME does.

If you look at it from a resistance perspective, you get these results. This shows that your MDK is out of spec.

Remember that this is a test sample of 1 and we are trying to do something new and different. We could be doing this all wrong.

 

I've tested my 2nd TB:

2 - 4 : 1048
1 - 7 : 1041

2-5 1834 - 1154
2-3 1952 - 1173
1-6 1965 - 1191
1-8 1812 - 1124

4-3 1228 - 1958
4-5 1165* - 1831
7-6 1229 - 1968
7-8 1163 - 1821

*4&5 pins are very sensitive, on different TB (as a whole) positions the starting value was changing in the 50 Ohm range.
Re-tested the 1st TB, got different values for 4&5: 1237 - 1865 instead of old 1040 - 1725.
Could've been my error during the first measurements. The values were not changing like in the case of the 2nd TB when I was moving around the TB.

Generously applied wire cleaner by ABRO. Interesting to see if values will change tomorrow.

 

Here is the updated Resistance table for the first MDK

Here are the test results from the second MDK

• All of the high resistances are within tolerance.
• All of the low resistances are not in tolerance.
• You have noted 50 ohm resistance jumps/changes between pins 4 and 5 with the MDK closed. This is a sign of a faulty MDK.

The M52TUBXX engine runs on the Idle control valve for lots of the low rev's operation. My testing has shown that for steady speed operation, the Throttle body does not start opening until about 50kph (30 mph). The throttle body does open during acceleration around those speeds, but the results are related to steady speed conditions. At a steady speed of 100 kph (60 mph), the throttle body is only open 12%. This means that the throttle body spends most of its time operating in the 0% to 30% opening range. This is the area of most wear on the carbon resistance strip and probably why you have detected damage on the second MDK at the start/closed position for pins 4 and 5.

I've been doing some more work on testing the MDK. It's not finished. Looks like I'm going to have to pull a known working MDK and do some testing to confirm my thinking.

 

Looks like I'm going to have to pull a known working MDK and do some testing to confirm my thinking.

That would be very helpful.

If anyone else has a working throttle body please post the resistance measurements, it would help in finding a way to diagnose it.

 

Had some time to test my cars with the Foxwell NT530 scanner with BMW software. Interesting results. Got all this data from the scanner. Still working my way through it, but thought that you may like to see it in in the raw.

Car was stationary during the tests, key in position 2 with the engine off.

 

I've just remembered that during resistance measurements when I was rotating the axe (which is connected with the cable) the values were always changing BUT when I was rotating the smaller metallic part (the one that overrides cable-axe position) on some pins the values were not changing. Is this a sign of a problem?

 

The metal arm that over-rides the cable cam is connected to the throttle valve/butterfly side. You were putting forces on the spring coupling between the butterfly and the cable cam in reverse. There will be some slop in the system, so by turning the system with reverse forces, the potentiometers will be turning slightly differently.

 

There will be some slop in the system, so by turning the system with reverse forces, the potentiometers will be turning slightly differently.

There was no change at all (for some pins).

 

Where the pins that did not change relate to the throttle potentiometers and the ones that did change relate to the pedal potentiometers?

 

I haven't noted which were the pins.

 

If you are having jumping resistance with the MDK closed try this.

• Fit the MDK to the car. Start it up and let the engine warm up to its normal operating temperature.
• Reach in and adjust the accelerator cable adjuster. Turn it counter clockwise until the RPM just starts to rise. Then turn it back a bit, so the idle is at its normal level (circa 700 rpm).
• Clear the trouble code and go for a drive. See if that fixed the problem. Let me know how it works out.

 

I have bought used wiring harness, cut the 10 wires leading to 10-pin connector and am about to re-solder that into my existing harness. Similar to the @Effduration's 4th suggestion. Was practicing soldering during these few days... Any tips before I ruin the harness is appreciated.

My cable is loose, there's no tension at all when gas pedal is in default state, the adjustment part is not functioning. Can this be a cause of the problem?
I'm going to use the MDK that's not having resistance jumping.

 

I have bought used wiring harness, cut the 10 wires leading to 10-pin connector and am about to re-solder that into my existing harness. Similar to the @Effduration's 4th suggestion. Was practicing soldering during these few days... Any tips before I ruin the harness is appreciated.

I am about to go thru this myself. I have a complete spare harness for my '99 E39 528i with M52tu. Rather than cut and solder, I think I am going to replace the entire harness with the used one I bought. I will put "Stabilant 22" or DeOxit on all the connections of the 10-pin connector for the MDK (throttle body).

This is more work, but I would rather not cut two harnesses if I don't have to... I don't mind having to replace the harness because I need to do the cooling pipes under the intake manifold anyway, and with the intake off, replacing the harness is pretty easy.

If this doesn't work, I will cut and solder the connector on my original harness per:

Electronic Throttle Faults & Repair

Diagnosing electronic throttle body faults and replacing its connector plug on 99-00 BMW 5 series.

www.frankies-bmw.com

 

The idea of adjusting the cable is to try and lift the potentiometer wipes just a little away from the damaged area that causes the resistance jumping.

That's a good idea to practice our soldering skills before attempting the harness. I'm sure there are you-tube clicks that will give you all the soldering tricks and tips.

There should be a rubber grommet on the "F" mount that the cable adjuster goes through. There was one case, where it was claimed that the lack of the grommet was the cause of the problem due to too much slack. Does your cable adjuster press into a rubber grommet on the "F" mount? The part number for the grommet is 35411164739.

 

Here is my situation with the cable:

 

It looks to me like your rubber grommet that is part of the bracket that adjusts the cable has perished. part number 35411164739 I think...but you might consider replacing it. I see them on Ebay

 

Another question related to soldering is where to cut existing wires from?
Compared to the used wires I have bought existing ones' colors are faded. I am not sure what to make of those faded colors (caused by heat, short? or just dirt...). Cutting from deeper position will make soldering more challenging.

 

Here are a couple of phots of how the cable should look. It looks like your cable has been replaced at some stage with one from a different car.

Have you tested the resistance of the wires in the harness? I suggest that you do, before you go the effort to change the plug.

• Locate the connector X60003 at the DME. It's the big 52 pin connector, number 3 counting from the fire wall to the bumper.
• Remove the outer black plastic cover, 2 tabs and the end.
• Back-probe next to the wires to get a connection. A metal paper click works. Do not front probe the connectors. You are likely to push the probe into the small connector and damage the connector. This just make another hard to find fault to locate.
• Attached is a PDF with a form that I use for another part of MDK testing. It gives the DME and MDK pin outs.
• If your digital multi-meter has a "REL" button. When on ohms, hold the probes together, when the screen say zero or near zero, push the REL button. This will give you a reading relative to zero. It makes the meter more accurate.
• Let me know what the harness resistance are. My thinking is that anything < 0.5 ohm is good.

 

Fair enough...I wasn't intending to hijack the thread..although I think any discussion of testing the MDK would be less than complete without a mention of the 10-pin MDK connector which seems to be a common source of problems...at least as common as a failed MDK.

 

I don't have a multimeter currently. And I haven't measured the resistances of the harness.

Currently it's the first time in the last couple of years that I was struggling with this problem that I can see something that is off: the state (faded colors) of the wires going into the connector. It may sound weird but I am excited about it. I have made some close up videos of the wires. I don't know if this is a big deal, you guys are more experienced, I'd like to hear your opinion. Also hard to decide from where to cut the old wires.

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