[PNWn55]

Hi everyone, I have a 2011 e90 335i and I keep blowing fuse 38 in the glove box. I've searched and searched and can't find what this fuse protects. It just shows an engine symbol on the little diagram card in the glove box. I have no idea where to start troubleshooting at the moment. There's nothing obvious under the hood. Thanks in advance!

[Serf27]

It’s showing the crankcase heater hose, ECM and o2 heater.
The crankcase hose is probably bad internally and shorting out.

[gbalthrop]

Originally Posted by PNWn55

Hi everyone, I have a 2011 e90 335i and I keep blowing fuse 38 in the glove box. I've searched and searched
and can't find what this fuse protects...

Nothing important, only your DME. I would presume the engine does NOT run when fuse blows?
This appears to be a case of 2011 N55 DME wiring & fuses being quite different from models to 2010. Since Bentley (which shows
F38 as powering O2 Sensor Heaters & Crankcase Vent Heater) was published BEFORE 2011 models came out, and ISTA shows
different circuits, I would trust (but VERIFY) ISTA.

Attached are ISTA ScreenPrints of circuits for Fuses powered by DME Main Relay (K6300), and F38 circuit.
Also attached is circuit for O2 Sensor Heaters (only two on N55?), powered Directly by DME, NOT via any dedicated fuse.

Please let us know what you find, or if you have questions on testing. Generally, one can test a circuit WITHOUT
wasting a lot of fuses, by simply measuring Ohms on circuit in relation to Chassis Ground, testing for short-to-ground.
George

[PNWn55]

Originally Posted by gbalthrop

Nothing important, only your DME. I would presume the engine does NOT run when fuse blows?
This appears to be a case of 2011 N55 DME wiring & fuses being quite different from models to 2010. Since Bentley (which shows
F38 as powering O2 Sensor Heaters & Crankcase Vent Heater) was published BEFORE 2011 models came out, and ISTA shows
different circuits, I would trust (but VERIFY) ISTA.

Attached are ISTA ScreenPrints of circuits for Fuses powered by DME Main Relay (K6300), and F38 circuit.
Also attached is circuit for O2 Sensor Heaters (only two on N55?), powered Directly by DME, NOT via any dedicated fuse.

Please let us know what you find, or if you have questions on testing. Generally, one can test a circuit WITHOUT
wasting a lot of fuses, by simply measuring Ohms on circuit in relation to Chassis Ground, testing for short-to-ground.
George

Thank you George! This forum has been a big help. I checked the oxygen sensors but they seemed fine (they're newer) and then found the pcv heater and it was ringing out to ground. I put a new one in and it also has continuity to ground but I put a new 30a fuse in and it runs! So I'm hoping it's fixed. I installed a bms catch can so my old pcv heater was just hanging out in the engine compartment cause it said to leave it plugged in. I taped up the new one up so no metal touches/grounds out to the frame- not sure what else to do with it. They said it'll throw a cel if I remove it. So I'm hoping it's fixed now. It Would blow the fuse instantly before. Thanks again!

[BSM-MSPORT]

What did this end up doing? I have a P0030 (2D0D) for open circuit with the o2 sensor heater and I already put in a new sensor. Learned that there is not a fuse which I now see is powered by the DME. Is there supposed to be a 30A fuse in F38? Because my F38 is a 15A...