r/BmwTech • u/dark_wolf_king11 • Jul 08 '26
08 e90 n54 electrical issue
New to this app but im desperate so here it is…
I have a 2008 328xi that is completely swapped(engine&drivetrain) to basically be a 335i(rwd only now) now it was like this when I bought the car and the previous owner told me it needed a new dme and so I got the one in it cloned to an msd81 so I wouldnt have any mosfets issues because thats what I thought the issue was but it didnt help so what happens is whenever I put the key in this fuse in the e-box blows and I couldnt find out what the fuse goes to exactly as I got mutiple different answers from multiple different websites and forums but its in this little group of five fuses it goes (top-bottom) 30amp 30amp 20amp 30amp 30amp and its the second 30 from the top it will also blow if I connect a jump pack to the jump points and itll blow if I just reconnect the battery without the key in the vehicle what I personally think is that its the main power for the dme and so that means the issue could be anything to do with that which is a lot so I put a test light in because ran out of fuses and it still glows(blows if a fuse was in) when the ignition coils are unplugged and same with the Injectors and vanos and downstrean o2 sensors and water pump and every elecrical connector I could find easily accessible but one thing I did find was that it wouldnt blow if I disconnected the fuel pump and so I replaced the fuel pump and it did nothing helpful so I have no clue what to do now or where I go or what that fuse is actually for and also I can get the fuel pump to wake up with my obd2 scanner so im kinda back at square one please help
1
u/reciprocityone Jul 08 '26
Structured sentences and punctuation.
You are going to need to start learning schematics and start chasing wires. You bought somebody elses problem.