HELP! Pulling my few remaining hairs out. N54

swellengear · 10-16-2023, 01:53 AM

Hi Guys, really hope somebody can shed some light:

The Car:
2008 135i N54, Catless DP, DCI, BOV, JB4 (MSD80 DME)

The Problem:
30BB - Injector Circuit Failure 4-6 or DME Internal Fault, and affiliated codes

How it happened:
Car was parked for 2 weeks, went to start it, and it misfired like crazy

What I've done so far:
Swapped coils, plugs and injectors from bank 1 to bank 2 - no change
Tested all wiring from injectors back to DME - all good
Tested all the injector ground wires - good
Measured all the mosfets in the DME, twice - all read identical, non are shorted

So now I am a bit of a loss. After lots of reading, it generally seems to turn out that one or more of the mosfets have gone bad in the DME, however, in mine, they all test fine. I'm also perplexed as to how it happened. Most people tend to report this error while driving. Mine drove like a champ, I parked it, and after starting it a while later, it gave me that error.

ANY insight or ideas will be much appreciated.

Thanks!!

4JawChuck · 10-17-2023, 08:51 AM

Since these cars have no real filtration on the fuel lines except for the sock in the tank I would suggest you have plugged injectors.

I’ve had fuel start to go bad (turn dark yellow) in under a month, I now treat all my fuel on every fill up because of how bad the fuel has become.

My elixir had been proven to work and after injector cleaning is done no more issues with misfires on multiple vehicles.

30ml of each these products added to the tank works, Marvel Mystery oil (breaks down carbon deposits), Seafoam (deposits and combustion chamber) and marine fuel storage additive.

My 128i with 60K miles had plugged/leaking injectors on 4 of the 6 that were tested before cleaning, one was so bad it constantly leaked fuel under pressure.

My wife’s Fiat fuel injectors took a few months of maximum doses of Marvel Mystery oil to get them clean, now it runs perfectly.

Todays oxygenated fuels oxidize very quickly so I don’t take anymore chances with storing it for any length of time.

I would pull your injectors and have them cleaned before you spend a bunch of time diagnosing issues, will to bet they leak..

swellengear · 10-19-2023, 04:59 AM

Thanks for taking the time to reply. I can rule out the injectors. The car will idle (badly) on bank 1 alone. As mentioned above, I swapped everything from bank 1 to bank 2. No change. It will idle, but only bank 1 is operational. (ie the injectors from bank 2 work when in bank 1)

I have sent the DME for testing at a specialist, and am hoping for news today. I will post an update as soon as I have one.

swellengear · 11-01-2023, 02:45 AM

**Update**

The ECU specialists confirmed that the MOSFETS were all in working order, but went ahead and replaced them with the upgraded units anyway. Unfortunately, this did not solve the problem. The ECU tested 100% on the bench, however, once fitted to their test vehicle, the fault was back. 30BB.

It ended up being a bad solder joint on the second board (located underneath the main board with the MOSFETS on it).

The car is now back up and running!

Happy days.

10-16-2023, 01:53 AM	#1
swellengear New Member 2 Rep 9 Posts Drives: 2009 135iS Join Date: Feb 2023 Location: Swellendam, South Aftica iTrader: (0)	HELP! Pulling my few remaining hairs out. N54 - 30BB SOLVED Hi Guys, really hope somebody can shed some light: The Car: 2008 135i N54, Catless DP, DCI, BOV, JB4 (MSD80 DME) The Problem: 30BB - Injector Circuit Failure 4-6 or DME Internal Fault, and affiliated codes How it happened: Car was parked for 2 weeks, went to start it, and it misfired like crazy What I've done so far: Swapped coils, plugs and injectors from bank 1 to bank 2 - no change Tested all wiring from injectors back to DME - all good Tested all the injector ground wires - good Measured all the mosfets in the DME, twice - all read identical, non are shorted So now I am a bit of a loss. After lots of reading, it generally seems to turn out that one or more of the mosfets have gone bad in the DME, however, in mine, they all test fine. I'm also perplexed as to how it happened. Most people tend to report this error while driving. Mine drove like a champ, I parked it, and after starting it a while later, it gave me that error. ANY insight or ideas will be much appreciated. Thanks!! Last edited by swellengear; 11-01-2023 at 02:45 AM..
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10-17-2023, 08:51 AM	#2
4JawChuck Private First Class 216 Rep 104 Posts Drives: 2013 128i SE Join Date: Feb 2023 Location: Canada iTrader: (0)	Since these cars have no real filtration on the fuel lines except for the sock in the tank I would suggest you have plugged injectors. I’ve had fuel start to go bad (turn dark yellow) in under a month, I now treat all my fuel on every fill up because of how bad the fuel has become. My elixir had been proven to work and after injector cleaning is done no more issues with misfires on multiple vehicles. 30ml of each these products added to the tank works, Marvel Mystery oil (breaks down carbon deposits), Seafoam (deposits and combustion chamber) and marine fuel storage additive. My 128i with 60K miles had plugged/leaking injectors on 4 of the 6 that were tested before cleaning, one was so bad it constantly leaked fuel under pressure. My wife’s Fiat fuel injectors took a few months of maximum doses of Marvel Mystery oil to get them clean, now it runs perfectly. Todays oxygenated fuels oxidize very quickly so I don’t take anymore chances with storing it for any length of time. I would pull your injectors and have them cleaned before you spend a bunch of time diagnosing issues, will to bet they leak..
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10-19-2023, 04:59 AM	#3
swellengear New Member 2 Rep 9 Posts Drives: 2009 135iS Join Date: Feb 2023 Location: Swellendam, South Aftica iTrader: (0)	Thanks for taking the time to reply. I can rule out the injectors. The car will idle (badly) on bank 1 alone. As mentioned above, I swapped everything from bank 1 to bank 2. No change. It will idle, but only bank 1 is operational. (ie the injectors from bank 2 work when in bank 1) I have sent the DME for testing at a specialist, and am hoping for news today. I will post an update as soon as I have one.
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11-01-2023, 02:45 AM	#4
swellengear New Member 2 Rep 9 Posts Drives: 2009 135iS Join Date: Feb 2023 Location: Swellendam, South Aftica iTrader: (0)	Update The ECU specialists confirmed that the MOSFETS were all in working order, but went ahead and replaced them with the upgraded units anyway. Unfortunately, this did not solve the problem. The ECU tested 100% on the bench, however, once fitted to their test vehicle, the fault was back. 30BB. It ended up being a bad solder joint on the second board (located underneath the main board with the MOSFETS on it). The car is now back up and running! Happy days.
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