2011 M3 Electrical Problem

[Jhunter]

I have an electrical power problem that has developed with my 2011 M3. It has been to the dealer once but they were not able to identify the cause.

For the last year I would periodically get a warning that the hood was unlatched. This would happen at random while driving. There would be a month or two between instances with the car driven daily. At all times the hood was properly latch. Turning off the car and restarting usually resolved the warning.

About six months ago, with no identifiable pattern, I would have instances with the car being completely dead, no start, no power door locks, no lights, no clock, nothing. This has happened about six times in the last six months. If the car was locked, and the unlock on the remote was pushed or the door handle was touched (comfort access), the alarm would go off. The alarm goes off even though the car has no other electrical power. I was not able to turn the alarm off with the remote or any other way. It would continue to sound until I guess it timed out.

Each time I had the no power condition, if I waited a period of time, sometimes an hour, sometimes a number of hours, and tried the car again, everything worked normally. The car started normally and the battery seemed to have full power. The only adverse effect was I had to reset the clock. The battery is less than a year old and was properly registered when installed.

After the first no power incident I had the car in to the dealer. The battery checked out fine and the only code was for a fault with the hood switch. The dealer's recommendation was to replace the hood latches and cables as the tech thought the driver's side of the hood was slight higher (1 or 2 mm) than the passenger side and maybe not activating the switch when closed. Since the hood switch is closer to the windshield on that side and given the distance and angle of the hood caused by 1 or 2 mm at the front, this didn't make sense to me. Their theory was also that the car was reading the hood as open, therefore not going to sleep, therefore draining the battery over time. The first time it had no power I did try to jump it. It did eventually start but I don't think it was due to the jumping more just the random passage of time as mentioned above. Every instance since then, I did not jump it, the power just mysteriously came back on its own after some time.

About a month ago I disconnected the hood switch to take it out of the equation. Everything was normal for about a month until another no power/alarm going off incident yesterday. I left the car at my business overnight, tried it a 9:00 am this morning, no power, tried again at 11:30 am, full power, car worked perfectly.

Anybody have any idea what is the cause/fix for this??

[MIKYZZ4]

Check for clean, tight connections at battery. The need to reset clock tells me that battery voltage/current was temporarily removed from the electrical system.

[bmwdirtracer]

What's really bad here is that the dealer can't tell you what triggered the alarm. An alarm trigger sets a code. A power-off episode sets many codes.. There's a device on your car called an "Intelligent Battery Sensor", and it keeps track of the state of charge, and improper discharges, of the battery.

The dealership (and top-of-the-line BMW indy shops) have a computer called ISTA, which will read and analyze stored codes, and guide the technician through a test plan for those codes. The CAS (Car Access System) will have codes, too.

And, well, there's the good old fashioned method, of just checking the battery voltage, preferably underhood, when you see the problem.

I'm disappointed in your dealership.

[MIKYZZ4]

I also found it odd that the dealership, with all the BMW electronics at their disposal, could not find any other clues to track down issue. I just assumed an inept,lazy tech or service dept. Just to be clear jhunter -this is an OEM factory alarm or aftermarket?

[Jhunter]

Yes the alarm is factory. The battery was installed by my brother who is a BMW tech. Connections are solid and 100% clean. He lives 700 miles away so he is not available to diagnose the problem.

The dealer tech seemed to be focused on a battery discharge problem. The first instance the car did restart with a jump after being connected a long time but I think this was a coincidence. With the second instance there was no jump. The power came back after a few hours and the car operated normally with no jump. I told the service writer this but they either ignored this or misunderstood. Since it has happened at least four more times since it was at the dealer I am sure it's not a battery discharge issue.

Based on what they told me the only code was for the hood sensor. After discussing with my brother I told them not to replace the hood latches. I paid for the diagnostic time. I am scheduled in again next week but I am trying to get ahead of the problem here so I don't pay for diagnostic time again with no resolution.

Thanks for your responses and insight!

[WadiM3]

Did your brother code the battery to the car ?

[Jhunter]

I assume yes. He's been a BMW tech for a long time and knows what he is doing.

[WadiM3]

Dont assume! Find out!!