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      12-06-2015, 07:01 AM   #1
rashad.mashtoub
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What caused my DME to burn (Mosfet) ?????

Hey Guys,

I have a 335i bmw e92 2008 model. I am running on cobb stage 1 + FMIC when suddenly last week i went WOT and got all types of codes and faults: Cylinder 4,5,6 misfires and internal DME failure and the car just stopped functioning.

I read couple of threads on how to fix the mosfet i got, however i want to know what caused my DME to fire up and how can I avoid the same problem in the future.

Thanks gents
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      12-06-2015, 09:35 AM   #2
stanlalee
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I've heard the problem is the shitty quality of mosfets themselves in various MSD80 DMEs. There is no preventative action you should have to take. Just another typical case of BMW incompetency in reliability.
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      12-06-2015, 09:51 AM   #3
rashad.mashtoub
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Do you suggest changing the spark plugs, coils and fuel injectors? Despite the fact that the BMW service informed me that they are working fine?

Any suggestions
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      12-06-2015, 10:07 AM   #4
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I've heard various forum tuners blame faulty/worn coils causing the mosfets to short after putting on a tune so who knows. I have 137K miles on original coils and injectors, tuned for 70k miles (07' MSD80 of course). Seems to be completely random based on luck.
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      12-06-2015, 11:04 AM   #5
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Quote:
Originally Posted by stanlalee
I've heard various forum tuners blame faulty/worn coils causing the mosfets to short after putting on a tune so who knows. I have 137K miles on original coils and injectors, tuned for 70k miles (07' MSD80 of course). Seems to be completely random based on luck.
Happens to completely stock cars as well. Replace all the midgets while you are in there to prevent from happening in the future.

Edit: mosfets not midgets. Damn spell check
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      12-06-2015, 11:30 AM   #6
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But it's the midgets running around in the DME that burn out the mosfets in the first place.......

Remove the midgets
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      12-06-2015, 02:49 PM   #7
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Replace all mosfets from digikey.com, then you will see if you need new coils/plugs, when you start it up.
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      12-06-2015, 04:02 PM   #8
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Just like all older bmws - e30's, e36, e46 etc, when the coils get really bad and short out they can cause the DME to go bad. Best to replace just the coils for now to be sure once you get a new one in that it won't instantly fry up again.

Had this happen on my e36 328is once. Wasn't fun.
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      12-06-2015, 05:25 PM   #9
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I had my DME go out on a wot pull also. My friend/tech told me it was from a faulty coil. We went ahead and replaced them all. Just my experience.
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      12-06-2015, 06:10 PM   #10
Sean978
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For reference; had a mosfet failure and did not replace coils or plugs. Car ran perfectly fine for another 15k miles until it was totalled. In an accident, that is.

Last edited by Sean978; 12-06-2015 at 06:11 PM. Reason: totalled in an accident. lol.
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      12-06-2015, 07:25 PM   #11
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Just had this happen to me. Sent my dme out to a place in Illinois for further inspection and repair. They verified what I had already tested, bad midget on cylinder 1 gonna have em all replaced. They charge $218. Company is SIA, you can find them on eBay.
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      12-06-2015, 07:44 PM   #12
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Quote:
Originally Posted by Papa_Lion
Just had this happen to me. Sent my dme out to a place in Illinois for further inspection and repair. They verified what I had already tested, bad midget on cylinder 1 gonna have em all replaced. They charge $218. Company is SIA, you can find them on eBay.
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      12-06-2015, 07:57 PM   #13
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these midgets are wrecking havoc on the DMEs lol
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      12-06-2015, 08:15 PM   #14
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Sadly, those midgets gotta stay, They switch the coils and injectors. Its those damned blown squirrels under the hood that are causing all the smoking issues. Those definitely have to go.
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      12-06-2015, 08:25 PM   #15
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I will suggest using a multimeter to check coil primary resistance. I am not sure what resistance should be, but comparing all should root out any that are out of tolerance. Also check primary to secondary resistance. It should read very high as in megohm or open depending on your multimeter. Mosfets are like any other switch in that after many millions of reps they will become unreliable. They can fail open or closed. If they fail open, the device simply does not work. If they fail closed, the device is constant on, which usually results in device failure. On the other hand, a failed device (as in low resistance creating high current) can lead to a mosfet failure. Mosfets can also be intermittent in nature. Hope this helps. They are easy to change, but to do it well, a hot air device should be used to avoid cold solder joints. Use rosin core solder and flux. Clean with alcohol when your finish.
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      12-06-2015, 09:54 PM   #16
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Quote:
Originally Posted by Stroker1 View Post
Mosfets are like any other switch in that after many millions of reps they will become unreliable
Not buying that. During the late 80s/early 90s I was into car audio and still have a few amps today from 91 working perfectly with rows of mosfets. Same car environment and I'm sure much hotter. I cant ever remember mosfets failing in quality audio equipment. But that's not why I'm not buying it. To the point these have been failing for YEARS on cars in question that are only 8-9 years old with not particularly high mileage. I don't see 2007-2008 cars from other brands ECUs self destructing. I could see i this was a 85' VW rabbit. Apparently failures aren't exclusive to MSD80s and older BMWs also fail.

Which brings me to a question I've never really thought of until now. Who makes these DME's? Bosch, Siemens? If so why are they reliable for every other brand but somehow with BMW not so much?
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      12-07-2015, 12:58 AM   #17
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Quote:
Originally Posted by stanlalee View Post
Not buying that. During the late 80s/early 90s I was into car audio and still have a few amps today from 91 working perfectly with rows of mosfets. Same car environment and I'm sure much hotter. I cant ever remember mosfets failing in quality audio equipment. But that's not why I'm not buying it. To the point these have been failing for YEARS on cars in question that are only 8-9 years old with not particularly high mileage. I don't see 2007-2008 cars from other brands ECUs self destructing. I could see i this was a 85' VW rabbit. Apparently failures aren't exclusive to MSD80s and older BMWs also fail.

Which brings me to a question I've never really thought of until now. Who makes these DME's? Bosch, Siemens? If so why are they reliable for every other brand but somehow with BMW not so much?
Typically SIEMENS is the most common DME/ECU for BMW
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      12-07-2015, 07:37 AM   #18
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Quote:
Originally Posted by Papa_Lion View Post
Just had this happen to me. Sent my dme out to a place in Illinois for further inspection and repair. They verified what I had already tested, bad midget on cylinder 1 gonna have em all replaced. They charge $218. Company is SIA, you can find them on eBay.
That's very steep! I paid $40 to have all 6 , replaced.
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      12-07-2015, 08:17 AM   #19
rashad.mashtoub
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So Im gonna change all of them at once instead of changing the burned ones only...But i should keep using my cobb with no problem at all right?

BMW service center told me that the all coils, spark plugs and fuel injectors are working fine, however i think im gonna change the coils as well...

Cheers guys
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      12-07-2015, 08:50 PM   #20
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[quote=stanlalee;19024119]Not buying that. During the late 80s/early 90s I was into car audio and still have a few amps today from 91 working perfectly with rows of mosfets. Same car environment and I'm sure much hotter. I cant ever remember mosfets failing in quality audio equipment. .

Cant compare mosfet function in an audio amplifier circuit(modulated analog ac waveform) to a mosfet function in a dc switching circuit as in an ecu controlling coils and injectors. The demands and device stresses are entirely different.

To the point these have been failing for YEARS on cars in question that are only 8-9 years old with not particularly high mileage. I don't see 2007-2008 cars from other brands ECUs self destructing. I could see i this was a 85' VW rabbit. Apparently failures aren't exclusive to MSD80s and older BMWs also fail.

At the risk of sounding like an apologist for BMW, I hold BMW engineering in high regard. That being said designs fail in service. BMW by no means has a lock on reliability issues. One needs simply to search for recalls and service bulletins for all manufacturers for 2007-8. You will find literally hundreds of repetitive issues with all makes. BMW responded to the known msd80 by a redesigned ecu(msd81). I find the high cost of ownership as offensive as anyone, but if you want to play, you have to pay............
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      12-07-2015, 10:29 PM   #21
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[quote=Stroker1;19029494]
Quote:
Originally Posted by stanlalee View Post
Not buying that. During the late 80s/early 90s I was into car audio and still have a few amps today from 91 working perfectly with rows of mosfets. Same car environment and I'm sure much hotter. I cant ever remember mosfets failing in quality audio equipment. .

Cant compare mosfet function in an audio amplifier circuit(modulated analog ac waveform) to a mosfet function in a dc switching circuit as in an ecu controlling coils and injectors. The demands and device stresses are entirely different.

To the point these have been failing for YEARS on cars in question that are only 8-9 years old with not particularly high mileage. I don't see 2007-2008 cars from other brands ECUs self destructing. I could see i this was a 85' VW rabbit. Apparently failures aren't exclusive to MSD80s and older BMWs also fail.

At the risk of sounding like an apologist for BMW, I hold BMW engineering in high regard. That being said designs fail in service. BMW by no means has a lock on reliability issues. One needs simply to search for recalls and service bulletins for all manufacturers for 2007-8. You will find literally hundreds of repetitive issues with all makes. BMW responded to the known msd80 by a redesigned ecu(msd81). I find the high cost of ownership as offensive as anyone, but if you want to play, you have to pay............
I don't disagree with most of what you said but for the life of me I don't get this concept of paying to play for basic reliability. I understand maintenance, parts, repairs and labor will cost more than a Nissan sentra. I don't think I should be paying for failures that occur grossly before industry standards. For example I don't have a problem with the cost of water pump replacement. I have a problem with them routinely failing at under 100k miles and leaving you stranded without warning. I don't have a problem with the cost of injectors, I have issue with the fact that not a single other car on the planet direct injection or not have injectors routinely/randomly needing replacement in a typical ownership period. I even understand German cars are fickled in general but you have to draw the line somewhere. I have 138K relatively issue free miles. I'm not complaining for myself but the others lol.
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      12-08-2015, 11:11 AM   #22
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[quote=stanlalee]
Quote:
Originally Posted by Stroker1 View Post
Quote:
Originally Posted by stanlalee View Post
Not buying that. During the late 80s/early 90s I was into car audio and still have a few amps today from 91 working perfectly with rows of mosfets. Same car environment and I'm sure much hotter. I cant ever remember mosfets failing in quality audio equipment. .

Cant compare mosfet function in an audio amplifier circuit(modulated analog ac waveform) to a mosfet function in a dc switching circuit as in an ecu controlling coils and injectors. The demands and device stresses are entirely different.

To the point these have been failing for YEARS on cars in question that are only 8-9 years old with not particularly high mileage. I don't see 2007-2008 cars from other brands ECUs self destructing. I could see i this was a 85' VW rabbit. Apparently failures aren't exclusive to MSD80s and older BMWs also fail.

At the risk of sounding like an apologist for BMW, I hold BMW engineering in high regard. That being said designs fail in service. BMW by no means has a lock on reliability issues. One needs simply to search for recalls and service bulletins for all manufacturers for 2007-8. You will find literally hundreds of repetitive issues with all makes. BMW responded to the known msd80 by a redesigned ecu(msd81). I find the high cost of ownership as offensive as anyone, but if you want to play, you have to pay............
I don't disagree with most of what you said but for the life of me I don't get this concept of paying to play for basic reliability. I understand maintenance, parts, repairs and labor will cost more than a Nissan sentra. I don't think I should be paying for failures that occur grossly before industry standards. For example I don't have a problem with the cost of water pump replacement. I have a problem with them routinely failing at under 100k miles and leaving you stranded without warning. I don't have a problem with the cost of injectors, I have issue with the fact that not a single other car on the planet direct injection or not have injectors routinely/randomly needing replacement in a typical ownership period. I even understand German cars are fickled in general but you have to draw the line somewhere. I have 138K relatively issue free miles. I'm not complaining for myself but the others lol.
+1

Also, the fact that the ps pulley could hit the subframe causing the belt to shred and get sucked into the engine and blow it up. Or the frequently cracking valve cover gaskets. Endless revisions on coils and injectors - just get it right! Rattling waste gates. Oh And Oil leaks, which I've accepted as a part of life when owning one of these beauties. I truly love my 335 but man, I think a lot about these cars and Bmw in general is truly crappy, and I don't recommend the brand for anyone buying used outside of warranty unless you do your own work. It's just not worth it.

Sorry for the rant... ready to get flamed by the community...
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