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I have a 2007 E61 M5 that I have owned for about 3 years. I became aware of the drain/flooding issues on cars with the panoramic sunroofs and this spring took the trouble to check the 4 drains. The front drains were fine but the rear ones didn't flow very well so I removed the valves at their ends and ran water through them until the water ran clear. I also cleared the drains under the scuttle and was pleased I had been able to do this preventive maintenance before I had any issues. What I didn't do was relocate any of the modules to higher ground....

A couple of weeks ago I was in Belgium and there was very heavy rain on the Saturday evening. I didn't use the car again until Sunday evening and everything was fine. I used the car on Monday during the day without issue. Monday evening 3 of us went out to dinner and immediately after I dropped the rear seat passenger off I got a self levelling system failure message. I figured it was the infamous E61 air spring compressor issue and drove back to the hotel. Tuesday morning the error was still there and the rear of the car was riding very high.

On the drive back to the UK I first got a tyre pressure system error (European cars use the ABS sensors, not special valves in the wheels). Then I got various yellow SMG, start assist, air bag and ABS/traction control errors and the idrive and speedo would momentarily die from time to time. I was able to keep going and the car ran OK but the errors came and went. They would flash up on the idrive screen but then go away again - the only ones that seemed to "stick" on the check control were the tyre pressure monitoring system and the self levelling system error. By the time I got home all the error messages were gone which surprised me but I suspected I had not heard the last of this issue. Even the rear suspension ride height was back to normal.

I removed the various covers and inserts in the trunk and found a small amount of water in the bottom of what would have been the spare wheel well. It really was small, perhaps a few tablespoons and no more so I mopped it up with a rag. When I restarted the car there were no error messages. But within a minute or so of driving I get SMG and and ABS errors which come up, stay for a few seconds and then go away. I also had the idrive momentary shutdowns as well. Otherwise everything seems to work just fine. The ride height is fine.

I have read the error codes with the Bavarian Technic SW and there are loads of errors but virtually all of them are listed as "not currently present".

I can clear all the errors with the Bav Tech SW but when I drive the car they come back and the various error messages flash up and then go away.

The car still has its original battery which has been in service for just over 7 years. It took a CTEK battery maintainer 12 hours to report the battery as fully charged. I then immediately drove the car and had no error messages over the course of about an hour. But when the car then sat for 6 hours and I drove it again the random errors returned. I attached a volt meter to the cigarette lighter and discovered that the errors flashing up corresponded to voltage spikes of up to 18 volts. Given that the problems went away with a fully charged battery and that it was the original battery I figured a new battery wouldn't be a bad choice.

But on the first drive with the new battery the same errors occurred. As the BMW dealer made me an offer I couldn't refuse on a new battery and I bought it from them and had them install it. The tech spoke with me and I described what had happened. He immediately went into the trunk and pulled apart the ride height control module and found signs of water or condensation damage. He suggests replacing the module and seeing what happens. With coding the module is about $750 so I'm not too keen to spend that kind of money without more confirmation that's it's really the problem. After all the ride height system seems to work and adjusts itself again.

I put the new battery onto the maintainer overnight and when I drove the car this morning for a few miles I had no error messages. It then sat for 4 hours and a few miles into the next drive the temporary errors returned as before. So by and large the new battery has made no difference.

Next I tried running the car without the ride height control module plugged in. Upon start-up I immediately got a ride height system error message - fair enough as the module's missing. And when I drive the car the same temporary errors occur as before. At idle the error messages don't occur - they only happen as I rev the engine or drive the car. That does seem to point to the alternator.

So what should I do next? I can obviously open the other modules in the trunk to see if there's anything wrong. But since everything seems to work OK without errors until a voltage spike occurs I'm not sure that's the issue. Should I replace the voltage regulator? Any help would be appreciated!
 

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I think you answered your own question, in your second to last sentence.

Several of us have experienced the same issues with voltage spikes and random errors. I replaced my original battery...voltage spikes continued. I went ahead and replaced my entire alternator, but you can just replace the regulator to see if that cures your spikes/errors.
 

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unlock the secret OBC menu and drive around with menu 9, you'll get a live voltage reading. Pay close attention to it, it shouldn't go much higher than 15V. Anything higher and the regulator needs changing.
 

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Change the regulator. It's like $100 and is a relatively easy DIY.
 

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Yup, it was the regulator. I ordered it last Friday and it arrived today. No more spikes - hooray!
I know this is probably old to you but did this really fix the problem or did the codes and spikes continue? I have been diagnosing my car and it led me to the same conclusion that the regulator needed to be replaced after all the spiking and random codes I have been getting. And my alternator was reading 17.2 volts when it began spiking. But for some reason I keep thinking maybe my ECU is sending the messages to the alternator and causing the issue idk just a wild guess thanks in advance!
 

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Discussion Starter #8
Yes, the regulator solved the problem. The auto electrical shop I bought it from said they have seen lots of failures. The CAN bus controlled regulator gets fried by the heat. You can replace it without pulling the alternator.
 
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