[olly335i]

Hi, I have a 2008 335i E91. It has been sitting around for about 2 months now, I have taken it for a couple of drives in between and started it a few times. Recently I went to take it for a drive and it was completely dead, no electronics in the car were working. After jump starting it, I went for a drive and got hit with transmission faults, abs faults, power steering, airbag, as well as coolant overheating (water pump not turning on), idrive turning on and off and the wipers turned on by themselves. I managed to crawl home in 2nd gear (trans wouldn't shift) and put it on a battery charger, however even fully charged with the engine starting super quick and flawlessly the lights still came up and I couldn't shift into drive. It seems to me that the car thinks it is at low voltage, so shuts off all systems except for those needed to run the engine, as well as headlights and other accessories perfectly fine I am going to try clearing codes tonight, as well as register the new battery I put in about 4 months ago. Is it just a case of doing what I just said or is this an IBS fault or even something bigger?


UPDATE: I have cleared codes, reset battery, unplugged ibs etc nothing works. Here’s the MHD codes

[Volasko]

Are you sure your alternator is making juice when running? You could be running completely off the battery when you're running. If the battery is the only thing providing voltage the car will die pretty quickly. Depending on the age the voltage regulator could be spent (ie. the bushing that sit on the slip ring are used up). You should see +14V when the car is running, anything less the alternator is isn't making up the necessary juice. Ignore all those other codes until you check this, clear and check again. Low voltage causes all sorts of chaos with respect to codes.

[olly335i]

Originally Posted by Volasko

Are you sure your alternator is making juice when running? You could be running completely off the battery when you're running. If the battery is the only thing providing voltage the car will die pretty quickly. Depending on the age the voltage regulator could be spent (ie. the bushing that sit on the slip ring are used up). You should see +14V when the car is running, anything less the alternator is isn't making up the necessary juice. Ignore all those other codes until you check this, clear and check again. Low voltage causes all sorts of chaos with respect to codes.

Thought it could have been that at first, but that doesn’t make sense when you think about how I can fully charge the battery with a charger, start the car fine and the lights still pop up as well as water pump not working etc. Also on the night it first happened, I jump started it and took it for a drive which was about 10 minutes. If the alternator wasn’t working, it would not have been able to run on the battery for that amount of time because the battery was pretty much empty.

[Brandoch]

In the second picture it says 17.82 volts, if that's the case your voltage regulator is shot.

[olly335i]

Originally Posted by Brandoch

In the second picture it says 17.82 volts, if that's the case your voltage regulator is shot.

Yep I just noticed that too, I’m going to check it with a multimeter and if it says the normal voltage i’ll get a new one 👍

[lookalikehuuh]

At over 17 volts I'm not surprised you are having tons of electrical issues. I would stop running the car immediately and at a minimum replace the voltage regulator if not the entire alternator.

[BRG_N54]

Originally Posted by olly335i

Yep I just noticed that too, I’m going to check it with a multimeter and if it says the normal voltage i’ll get a new one 👍

I think the seasoned veterans here have already done the diagnosis for you. As advised, I would not run the car any longer and order up a new Bosch voltage regulator ASAP, only $50US, cheap fix.

[olly335i]

Originally Posted by BRG_N54

I think the seasoned veterans here have already done the diagnosis for you. As advised, I would not run the car any longer and order up a new Bosch voltage regulator ASAP, only $50US, cheap fix.

I’ve used a multimeter on my car and have confirmed that it must be the voltage regulator. As it started, The voltage was 16+ but as the revs dropped it came down to 14.6. So the voltage is dependant on the rpm meaning it must be V Reg