DME issue 750

[1999750il]

Hi all,

So it finally happened...my SES light came on after I had an Autel scanner connected to my 1999 750il with 116k miles. I used the scanner to simply scan the codes and I tried to test the ABS pumps by using the bi directional software of the Autel 908TS.
While I did hear the ABS pumps when I commended them on....right after this test..the SES light came on and the only code I could read was 8C...torque imbalance. In an attempt to clear the codes....I also used the Autel scanner to CLEAR the adaptations on DME1 DME2 and the transmission computer (AGS). After I cleared all 3 computers..I attempted to drive the car and noticed that there a SEVERE lack of power...it felt as if it was running on only 6 of the 12 cylinders.
The car cranks fine and starts up but idles a little higher and the SES blinks about 6 times at start up and then remains on steady. Of course the blinking means there is severe misfire that could damage the cats.
I also tried removing the battery cables from both batteries and hoping the computers would reset themselves overnight...but that didn't happen. I also tried resetting the throttles by KOEO and depressing the gas pedal..but nothing.
I know that the trans failsafe mode would make the car respond like this by shutting down half of the cylinders but there is no warning on my dash for it.

I have done extensive repairs to this engine..both MAFs replaced 3 years ago and throttles cleaned, both caps, rotors, all wires and plugs, coils replaced. Crank sensor and all 4 02 sensors replaced 4 years ago.

I finally take it to a BMW dealership and at first they said they were able to clear the code with their software and the car was working on all 12 cylinders...but a few hours later they call me to say the second test drive had the condition come back. They claim they hooked the car up to 2 different BMW software systems and that neither on of the them could get communication from one of the 2 DMEs.
According to the tech at the dealership...one of the DME is not communicating ANY of the parameters like throttle angle and he believes this indicates it not communicating and therefore the engine is only running on 6 of 12 cylinders. Along with this they also swapped the MAF sensors and verified that both throttles were working and getting hung up. They also checked all grounds for both computers. The dealer is stumped and reaching out to other technicians at BMW headquarters for advice. He claims BUT is not 100% certain if the issue is a bad or corrupt DME. Seems kind of silly to me that the dealer and a 30 year veteran mechanic working there cant determine with any amount of certainty whether or not a computer is actually working properly.

I'm still waiting to hear back from the dealer about their next move but they did mention that to replace one DME would be about $2700...and they aren't sure if that would correct the lack of power issue.

Not exactly sure if my clearing of the DME and trans computer adaptations could have caused this mess but I cant think of any other possible reason.

Is there anyone out there that had a similar issue with losing half of the engine power.

Thanks
Rick

[xboss]

I bet their fancy new computers cannot read the notoriously hard to talk to 750 DME's

True serial ports and ADS serial cables for our cars!

[asianvenom]

I bet their fancy new computers cannot read the notoriously hard to talk to 750 DME's

True serial ports and ADS serial cables for our cars!

Yes the round 17 pin under your hood...Amazon have it for a few bucks.

[psjr]

Usually losing one bank is due to a bad coil - you have replaced them already but could be worth another look.
Have you inspected the DME plugs and wiring to make sure they haven't been corroded or damaged?
Since the V12 was a pretty rare thing, it might not be fully supported by the latest dealer software as others have suggested.
Another thing that there are 2 of is crankshaft sensors.

After resetting EML adaptations (not sure what there is in the DMEs to reset), this is the procedure to calibrate the throttles, which may have to be done multiple times until it takes:

1. Turn ignition to position 2, wait 3-5 seconds
2. Push the throttle pedal all the way down and activate kick down switch, hold it for 3-5 seconds
3. Let off the pedal completely, wait 3-5 seconds
4. Push the throttle pedal all the way down and activate kick down switch, hold it for 3-5 seconds
5. Let off the pedal completely, wait 3-5 seconds
6. Turn off ignition, wait at least 10 seconds.

[1999750il]

Hi PSJR,

Thanks for the advice. I did find the thread you referenced about the throttles and have tried it several times. The Autel scanner I was using did have options to clear dme1, dme2 and the ags...which I did in hopes of clearing the SES light and restoring the power to the engine. What I am not certain about is what needs to be done after resetting these computers. I figured this would reset all 3 of them to factory specs and after some driving.....they would relearn driver inputs. I drove nearly 50 miles with no success. I believed the issue was the DMEs not communicating with each other and/or the trans computer and that's when I decided to bring it to the dealer hoping they would be able to determine what the cause is. They claim that one of the DMEs is NOT displaying any parameters or PIDS but the other is. While this would definitely cause a lack of power...I would think there must be a way to verify if the DME is fried or corrupt or if its simply a matter of it NOT communicating with the DME that is working.

I'm surprised that the dealer states they used a new and older version of their software and both were not able to pick up ANY PIDS from one DME. I am even more surprised that they cant determine with certainty whether the supposed BAD DME can be reflashed or if must be replaced. The head technician is not even sure if replacing the DME will solve the lack of power issue. He claims that they were able to verify that both throttle plates were fully opening and closing without any binding. Since this is a drive by wire that would tell me that both DME should be functioning since both throttles were responding and opening and closing as they should. I assume that each throttle is controlled by a separate DME but Z I am not sure if that's the case.
I know I had replaced one of the crank sensors 4 years ago and will suggest that the dealer look into that. I will also inquire whether they attempted to unplug the "bad" DME and see if its indeed a corrosion issue.


Thanks again for the suggestions

[psjr]

The throttles are controlled together by a separate module I mentioned above, the EML.

[xboss]

The can only talk to one DME part is a common problem with 750's so I would not jump to the conclusion that it is dead. I would look for a New York Bimmer guy that has DIS and INPA running or get the software running yourself.

[1999750il]

Hi PSJR and Xboss,

I appreciate the good advice.
According to the dealer....they believe one of the DMEs is NOT reporting ANY data to their scanners. They tried using both the new and older version of the BMW diag software.

Since the technician is still not certain if replacing the DME will correct the lack of power....I was thinking of suggesting that they swap they unplug and swap the DMEs and see if the scan tool will read the data pids then. Since my car has 2 DMEs and I believe they have the same part number....12147509323...as long as they're both flashed or programmed with the same software...I believe its possible to swap them and see if the "no communication" issue follows the suspect DME.
Since both throttle plates do move in unison and open and close all the way without binding...I believe the EML is functioning correctly.

Please let me know what you guys think....based on my knowledge swapping the DMEs should pinpoint the issue or at least reveal if the connectors on the suspect DME has corrosion.

Thanks for all your help

[1999750il]

Hi guys,

Since these cars have 2 DMEs that have the same part number but control different engine modules....they must be both be flashed at the dealership with different coding. If that is the case...I will not be able to simply swap one DME in place of the other and see if the scan tool reads differently? According to the BMW dealer....they claim the second DME is not reporting any engine data like throttle plate angle, 02 sensor, etc. After doing some research online, I believe they are only seeing the data stream from one of the DMEs due to the machine they are using. Many believe that the scanner needs to use a ADS connector AND a serial cable port not USB in order to read BOTH DMEs separately.
I am not totally certain of this is true....but if it is...how sad is it that the dealership isn't aware of this!!
If anyone can shed some light on this lack of power issue....after I reset both DMEs and the AGS....please chime in.

Thanks
Rick

[psjr]

I can read both DMEs with my USB cable and DIS (hooked to the under-hood connector with a 16-to-20 pin adapter that I modified with an extra ignition detect wire).
DIS is really the best software to use for 750s. The dealer machine that runs DIS is called a GT1; you can see if that is what they are using.

[1999750il]

Hi PSJR,

Thats great information...thank you!!!
I will reach out to the dealer and ask what system they are using.

I assume that both DMEs are programmed or flashed differently so simply swapping them may not be an option?

Thanks again for the great help

[1999750il]

My car has been at the BMW dealership for over 2 weeks for a lack of power issue and they are still no closer to finding the issue!!
Prior to bringing the car to the dealer...I attempted to correct the issue by resetting adaptations on both DMEs and the transmission computer (AGS) by using my Autel scanner 908TS...but this didnt help
The problem is a severe lack of engine power but the car does crank and start....it seems to be running on 6 of the 12 cylinders! Similar to a trans failsafe code but I have no such message on my dash.
As stated above the car has had extensive repairs...and most sensors have been replaced. The only trouble code that comes up is for torque imbalance.

Initially the dealership was not able to get ANY reading from DME number 2 and believed that my resetting of the DMEs may have created some sort of issue. They suggested swapping the DMEs and reflashing them to their new locations. This didnt work either and they still cant read DME number 2. They claim they also checked the ground wires and connectors and they seemed fine.
At this point they are stumped and not certain how to proceed.

Has anyone on this forum had something similar happen? I realize that in order to be able to read both DMEs ...the dealer may have to use ADS box and a serial connector. When i spoke to the tech at the dealership..he stated their tools use a LAN connection...not certain if that is sufficient to be able to read data from both DMEs. Its odd that even with the swapping and reflashing of both DMEs..they still are not able to read ANY data from DME #2.
If any techies on here..please let me know what you think of this odd situation.

Thanks
Rick

[xboss]

I recall a post about 750 DME relays going bad and causing one DME down like this. The dealer should have checked though.

So the one DME will not read in any position? Because if they swapped and flashed the one that will not read, it should have changed sides and become DME #1 instead of #2

If the problem followed over to the other bank's DME being the dead one then you need a DME off ebay for $100 but the dealer will not work with that I bet. You would have to bring it back for a flash probably.

[1999750il]

My car has been at the BMW dealership for over 2 weeks for a lack of power issue and they are still no closer to finding the issue!!
Prior to bringing the car to the dealer...I attempted to correct the issue by resetting adaptations on both DMEs and the transmission computer (AGS) by using my Autel scanner 908TS...but this didnt help
The problem is a severe lack of engine power but the car does crank and start....it seems to be running on 6 of the 12 cylinders! Similar to a trans failsafe code but I have no such message on my dash.
As stated above the car has had extensive repairs...and most sensors have been replaced. The only trouble code that comes up is for torque imbalance.

Initially the dealership was not able to get ANY reading from DME number 2 and believed that my resetting of the DMEs may have created some sort of issue. They suggested swapping the DMEs and reflashing them to their new locations. This didnt work either and they still cant read DME number 2. They claim they also checked the ground wires and connectors and they seemed fine.
At this point they are stumped and not certain how to proceed.

Has anyone on this forum had something similar happen? I realize that in order to be able to read both DMEs ...the dealer may have to use ADS box and a serial connector. When i spoke to the tech at the dealership..he stated their tools use a LAN connection...not certain if that is sufficient to be able to read data from both DMEs. Its odd that even with the swapping and reflashing of both DMEs..they still are not able to read ANY data from DME #2.
If any techies on here..please let me know what you think of this odd situation.

Thanks
Rick

[1999750il]

Hi xboss,

the original issue was with DME 2 and even after they swapped and reflashed both DMEs they are unable to read data from DME2. Since they swapped and reflashed both DMEs and the problem still exists...that should rule of a faulty DME. They claim they also checked the wiring and ground of DME 2 and they seemed fine. They also confirmed that both throttles are moving and not binding. I realize these cars are difficult to diagnose but with their software I thought they would be able to determine if it was a simple faulty ground or power issue or like you suggested..a DME relay.
Thanks again for your advice.

[Mayorchuck]

Threads merged and title updated. One thread per issue please. Hard to keep up with what you have tried and advice given otherwise.

[psjr]

I just saw your post in an unrelated thread that mentioned the OBD port cap not being in place.
In general, the cap does need to be present on one diagnostic port in order for the other to work.
You can take a look at the caps for them and see that they have some pins connected and a resistor, so the cap does affect the system.

[1999750il]

Hi psjr,

Thanks for the comment.
I remember seeing a thread that mentioned that the port caps do need to be in place in order to have the other diagnostic port function properly.
I had removed the 16 pin port cap in the middle console when I connected my Autel scanner to it and left it off when I dropped off the car to the dealership.
I would imagine that they would have known to check for a missing port cap once they were unable to get any data from DME#2 even after they swapped and reflashed both DMEs....but I guess I cant assume that.
I am not certain that a missing cap port on the 16 pin diagnostic connector will prevent the 20 pin under hood connector from displaying the ANY data from DME#2. And while the missing port cover may have an impact on what data can be read by the scanner...I dont believe that a missing port cap would cause the engine to run poorly. Regardless though...having the dealership see data from both DMEs should be beneficial in giving the technician a direction of what is causing the loss of power.

Unfortunately the car is still at the dealership and I am unable to confirm whether or not they replaced it before connecting to the 20 pin connector under the hood.
I will contact the dealership today and pray that the technician will accept the call and tell me the truth about whether or not they actually replaced the 16 pin port cover prior to hooking up their dealer tool to the 20 pin connector.

If someone can answer whether or not the missing port cover would have an impact on reading DME#2...PLEASE reply.

Thanks to all for the valuable advice I've received here.

[Mayorchuck]

Paul, is there a fuse carrier for each DME and if so, would a blown fuse cause any issues with diagnostics?

[psjr]

Paul, is there a fuse carrier for each DME and if so, would a blown fuse cause any issues with diagnostics?

Good question - the WDS is pretty confusing on the subject, but it does show that there is one fuse they share in the fuse carrier, and one not shared - the bank 2 not shared one also powers injectors, purge valve, and MAF for bank 2, and also connects to the AGS, so it would probably show transmission computer issues if blown. Definitely a quick and easy thing to check though, good idea Chuck.


I also did some research on the OBD cap question. The OBD port won't work without the under hood cap, but the under hood port doesn't look like it depends on the OBD cap.
Additionally, if the dealer software can connect to the EML and AGS, then it should be able to connect to DME 2 which uses the same diagnostic line.

I think checking the tan fuse carrier in the E-box is a good next course if the dealer somehow missed that.

To check if there is a diagnostic wiring issue to DME 2, check for continuity between pin 3 of the plug of DME 1 nearest the engine and the same pin of the same plug of DME 2.

[chrisn7]

I just saw your post in an unrelated thread that mentioned the OBD port cap not being in place.
In general, the cap does need to be present on one diagnostic port in order for the other to work.
You can take a look at the caps for them and see that they have some pins connected and a resistor, so the cap does affect the system.

This is correct that one cap always has to be in place because there is wiring between the two ports, so that if both caps are off diagnosis of DMEs will not be possible. At the 20 pin cap, if the board with the pins is removed you can see the hidden links between certain pins.

[1999750il]

Hi Paul, Chris and all,
thanks for the information.....you guys and this forum have given me great insight..and I truly appreciate your help

Chris ..just to confirm...in your opinion it would be necessary for the 16 pin cap to be installed in order for the 20 pin under hood connector to properly display the data from either dme2 and perhaps the eml and ags modules as well
if this is true....it would explain why the dealer is still unable to read dme2 even after swapping and reflashing
both dmes
I will ask the dealer to verify the tan-fuse carrier in the e box as well as both dme relays and pin 3 on both Dmes
i have always believed that the lack of power is due to some sort of miscommunication between the two dmes or between the eml and the dmes
i am hoping that once I contact the dealer and have them replace the 16 pin cap connector they will finally be able to read dme 2 and then determine what is causing my lack of power
please advise if there is anything else I should be looking for or advise the dealer to check
have a good evening
rick

[psjr]

I disagree that the OBD cap inside the car is a potential issue.

[1999750il]

Hi Paul,

Thanks for the quick reply. I will contact the dealership tomorrow and ask that they replace the missing OBD cap and see if that allows their scanner to display the data from DME#2. I will also bring up the other point regarding possible DME fuses, relays and pin#3 that I believe allows the DMEs to communicate to one another? If neither of these are the issue....I guess its worth looking into the EML or AGS modules not communicating or properly synched??
I would have thought an engine that does start and run and being able to read data from DME#1 would have given the tech at least a direction of where to start looking for the issue.
Thanks again for your advice and I will report back their findings.

[chrisn7]

As I mentioned there are links in the 20 pin cap hidden from view; there is also a link in the 16 pin cap; the 20 pin plugs home users plug in to the 20 pin socket also have links between pins. This makes understanding what the connections are a bit complicated.

Probably irrelevant, but sometimes the pacman engagement in the 20 pin cap cap gets damaged by ham fisted techs, and the cap gets replaced - but the V12 and V8 caps, although superficially the same, have different pcb/pin arrangements.

Where both 20 pin and 16 pin ports exist, the 16 pin is not fully wired, there being only 4 wires present, two of which are ground wires. These two are both connected to pin 19 on the 20 pin. Now its not very clear in the WDS what one of these actually grounds, so I would ensure that the 16 pin is in place if using the 20 pin. Every reference I have come across suggests that one cap or other must be in place.