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Voltage drop to 11.9v randomly
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07-20-2018, 05:55 AM | #45 | |
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S1CDA Source: https://www.e90post.com/forums/showp...49&postcount=6 |
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07-28-2018, 06:45 PM | #46 |
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Im having the same flipping issue. I took out jb4 i changed battery with genuine bmw and registered it i changed negative cable with ibs sensor i changed alternator cleaned battery cable connections at transfer point in trunk and today driving hard testing new ibs sensor car works fine until pushing it for about 15 min and voltage goes from 13.85v to 11.9v then bsd codes come up....driving me absolutely insane. Sitting in the driveway re registered battery just cause....max ac on voltage drops to 12.9v goes back up to 13.85v....shut ac off...voltage increases to 14.35v....did this for about 30min on idle....not a SINGLE ISSUE....driving it decides to go on the frits....i cant figure out what it could be unless my battery is toast....i changed the battery because it died a while back to find theres water in the trunk....cleaned corrosion changed terminals changed starter to encounter these issues then removed jb4 because had no issues while jb4 was OFF....still had the problem....changed ibs...same problem....now sitting idling with ac on and off works fine....going to drive some more tonight...wish me luck
Last edited by jus2sikwitit; 07-28-2018 at 07:16 PM.. |
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07-29-2018, 07:39 PM | #47 | |
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07-29-2018, 07:42 PM | #48 | ||
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07-30-2018, 09:41 AM | #49 |
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could be the ecu also. the BSD line comes from the ecu and something is happening in the ecu thats tell the alternator to stop charging. i think i saw a post from one guy who disconnected the bsd line from the alternator and it didn't have issue with voltage freaking out. i didn't try it. but maybe it's worth a shot.
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07-30-2018, 09:45 AM | #50 | |
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07-30-2018, 12:33 PM | #51 | |
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08-01-2018, 08:41 PM | #52 | ||
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08-01-2018, 09:40 PM | #53 |
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I'm having the same issue as the OP. Car is in the shop now and will update if resolved.
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2011 E90 335i M-Sport, PPK, cp-e CP, Helix stepped FMIC, xHP stage 3, Wagner catted DP, MHD stage 2 E30, GFB DV
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08-03-2018, 11:50 AM | #54 | |
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yea man i hope they find something. it will help many |
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08-05-2018, 09:34 AM | #55 | |
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My car is still in the shop with a very competent tech who is going down the diagnostic path and I'm about to go down there and completely remove MHD. I have had the issue on both stage 0 and stage 2, so I mean completely uninstall it.
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08-06-2018, 08:58 AM | #56 |
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Went to the shop this morning and uninstalled MHD, drove it for about 20 minutes with voltage meter hooked up, including at least a dozen WOT pulls. This would have previously caused BSD codes, loss of comm with alternator (and therefore drop to 12V battery voltage) and limp mode without fail. Without MHD, no codes, no limp mode, no voltage drops.
It only took $500 worth of diagnostic time at two shops plus this forum to figure it out, lol. Even though my tech and I are 99% sure that the tune is the problem, I'm going to reinstall MHD later to see if the issues come back. Then uninstall again to prove that they go away. Then I will reach out to MHD.
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2011 E90 335i M-Sport, PPK, cp-e CP, Helix stepped FMIC, xHP stage 3, Wagner catted DP, MHD stage 2 E30, GFB DV
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08-07-2018, 08:57 PM | #57 | |
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But so far it seems like most reports are from mhd guys. Maybe some food for thought. mhd guys are pretty helpful, I'd still try to reach out to them. Last edited by racermp; 08-07-2018 at 09:07 PM.. |
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08-07-2018, 09:33 PM | #58 | ||
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Did you happen to be running the BMS cowl filters with the factory cowl removed?
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2011 E90 335i M-Sport, PPK, cp-e CP, Helix stepped FMIC, xHP stage 3, Wagner catted DP, MHD stage 2 E30, GFB DV
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08-08-2018, 06:58 AM | #59 | |
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08-08-2018, 08:00 AM | #60 |
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That's a good thought. I'll check that out. It should throw a code if the fan quits altogether, but could be blocked by cobwebs or something. I wonder if DME temp can be monitored.
Thanks for continuing to engage on this even after you sold the car, lol.
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2011 E90 335i M-Sport, PPK, cp-e CP, Helix stepped FMIC, xHP stage 3, Wagner catted DP, MHD stage 2 E30, GFB DV
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08-08-2018, 10:04 AM | #61 |
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Haha no prob. I still have my N55 X5 so I'm active. Yeah solving this will help quite a few.
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08-26-2018, 05:55 PM | #63 |
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UPDATE - I've driven for about 2.5 weeks with MHD uninstalled and haven't had any limp mode. Had a central registry error that I think was due to battery registration being lost during the limp mode craziness, so re-registered battery and it hasn't come back.
Then decided to reinstall MHD stage 2+ on Thursday (still v1.24) and BSD codes immediately came back with WOT pulls. However, it didn't go all the way to limp mode this time, I think due to the milder temps we're having, furthering the idea that this is heat dependent. In the freeze frame data from Carly, the thing that stands out to me is voltage readings of 40-60V at the moment codes are set off. How is that even possible? I sent an e-mail to the MHD guys this morning hoping for some assistance troubleshooting. Stay tuned!
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09-15-2018, 01:48 AM | #64 |
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Wow.. you guys are still having this problem?
I had it with no MHD but latest BMW software. In the end i just stopped monitoring the voltages because it was causing unnecessary anxiety. If no control units log undervoltage faults and everything else behaves normally, i just put it down to part of the brake energy regeneration behaviour. The more frequently the car is used for medium to long journeys, the more likely it will occur due to the battery being maintained at a higher SoC. But those of you with MHD and experiencing limp mode etc, that might be worth discussing with MHD. |
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09-15-2018, 11:28 AM | #65 |
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Yeah, I'm still dealing with it. It can happen with or without MHD, but mostly with. I reached out to them and the suggestion was to look for a bad ground, but I just haven't had time yet.
I think our problem is the same, but yours hasn't progressed to the point of limp mode. Sometimes I get the BSD codes only without limp mode, which causes the alternator to stop producing voltage until a shutdown/restart. But the more I watch the other codes I'm getting, the more I think the BSD codes are a red herring. Yesterday, for example, I got a limp mode with BSD codes, but also about 15 other codes from various sensors (wheel speed sensors, steering sensors, etc), all saying that there was over voltage. Freeze frame data confirms that there was at least a split second of over voltage. As it only happens when it's hot and under heavy load, it leads me to believe that there is a short or insufficient ground somewhere that only surfaces under those conditions. My two front running ideas are: 1) Main engine ground strap going bad 2) Battery positive to fuse box connection going bad; there was a recall on this for over 500k E9X cars, but dealer says mine is not included. Thanks for the reminder. I'm going to look at the ground strap today as it's easier and cheaper.
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2011 E90 335i M-Sport, PPK, cp-e CP, Helix stepped FMIC, xHP stage 3, Wagner catted DP, MHD stage 2 E30, GFB DV
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09-15-2018, 10:00 PM | #66 |
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Well, the ground strap wasn't the problem. Replaced it with a 4 gauge cable from AZ, then went straight out and got limp mode within a couple pulls.
So I broke down and pulled the fuse box to inspect the positive battery cable connection. Hard to say for sure, but it does kind of look like a bit of discoloration on the terminal. It's still tore apart, but I will try to make the connection tighter tomorrow and see what happens. I'm curious, has anyone else having this problem had the recall done for the battery to fuse box connection?
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