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      08-20-2012, 10:25 PM   #1
Roy Cormier
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Drives: Single Turbo 335i
Join Date: Feb 2012
Location: Green Bay, WI

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Smile Repairing a 'fried' N54 MSD80 DME

So a couple weeks back I was out for a nice Sunday drive in my 335i, I downshifted into 3rd, floored it, and heard an insanely loud backfire. Then that damned half-engine light comes on and the car barely makes it home.

After reading the codes with the Cobb Accessport I decided to probe the pins on the DME connector to try to figure out what was going on.

The Transistor for injector #5 was toast, and after I saw what a replacement DME would cost from the dealer I figured I better just fix it myself. I took the part number off the MOSFET, spent $2.00 for a new one from digi-key and after a little bit of work with the hot-air gun I was back in business.

I was getting the following codes:
30bb - DME digital motor electronics, internal failure
29d1 - Misfire Cyl 5
29d2 - Misfire Cyl 6
29d0 - Misfire Cyl 4
29d9 - something about misfiring with low fuel level
29cc - Misfire Multiple Cylinders

So heres a few pictures in case anyone is unfortunate enough to have a similar problem occur.

Transistor pins were shorted together

Transistors labeled:

I stopped taking pictures after this point. But basically you just remove the bad MOSFET and install a new one in its place.

Then after everything was closed back up, it started and ran great.
Single Turbo E92 BMW 335i | | My YouTube channel

If you can leave black marks on a straight from the time you exit a corner till the time you brake for the next turn....... Then, you have enough horsepower.

Last edited by Roy Cormier; 03-16-2017 at 02:22 PM. Reason: updated picture links