car just totally died

[AlpineAce]

Hey Guys, Im new here, My previous car being an e39 540.

So I got this 06 4.8is this past spring. and a handful of minor issues, but it was fairly reliable. until a couple weeks ago, when at a stop light it started to freak out. First I got "trans failsafe"... I drove through the stoplight about 100 yards and the rest of the dashlights started to go on light a chrismast tree. I pulled over. and nothing was repsonding. I could press the gas pedal and it did nothing, a few minutes later it finally dies.

turning it off and back on, I got the alarm going off and it was asking for a "code" with time clock.

next day seems like the battery was almost dead, (but it was started and ran like normal for at least 15min before this happened) Tried to jump it at the contacts in the engine bay and saw a spark and smelled a whif of burned electronics, and now gets no power through those contacts.

So I manually opened the rear hatch and connected directly to the battery where It did get power, with my jump box. But again turning the key just sets of the alarm and ask for the code


(BTW is there anyway to disconnect the siren??, that is irritating as hell)

really need to get this running again!!

thanks!

[80stech]

Not sure if the V8s are different but on the sixs I think the jump terminal also acts as a splice for the starter/alternator so might want to check that. There is also a BST (eme rgency disconnect) at the battery that will limit what works if it's blown or comes loose. Alternator and /or battery might be a problem.

[andrewwynn]

Symptom of failing alternator. The computer will shut off non essential loads to try to keep the engine running so a light or two will come on at the dashboard then the engine will kill.

Never jump from the battery use the jump points in the front.

If the BST is blown/disconnected you'll get no power to the starter or alternator but also will happen if the terminal bolt at the positives "B+" is loose. About once every two years a thread on xo will result in bad alternator symptoms ends up being loose B+ bolt.

Measure voltage at B+ and make sure it's tight then charge the battery full not just jump start and see if once started will it bring voltage up to high 13 like 13.6 ± 0.2

You can monitor voltage real time with the hidden OBC menu. I don't recall which sub menu but there are full lists easy to find with a web search.

[oldskewel]

The whole story, I think, could be explained due to a failed alternator. But it could also be a battery or wiring failure.

Voltmeter measurements would help a lot.

Burn smell could be coming from the alternator if toast. But could also just be from the spark from connecting power to a near-dead battery.

Do you have a battery charger to charge it up? Doing that as a first step would make the rest of the debugging a lot easier (vs. near impossible). Or a spare battery to swap. Or a new battery if you are due anyway (but if doing that, don't assume you are done; confirm the alternator is good, which it probably is not).

Regarding the constant alarm, I know just how it is . Problem is that system voltage is high enough for the alarm to work, but low enough that it is confused and sets off the siren.

One approach is to disconnect the battery and charge it up fully before reconnecting.

But what I do in this alarm situation (where I know the only problem is a near depleted battery), since I try to keep a good spare battery in the garage, is to connect the battery charger to that good spare battery, and then jumper cables from the good spare battery to the X5 at the jump points.

In that setup, the spare battery maintains voltage while the X5 battery gets charged by the charger, keeping the alarm from going off. I'm sure the neighbors are happier this way.

Agreed on the other comments, especially the note about how the I6 vs. V8 major wiring (starter, alternator, jump point) are completely different from eachother - so be aware and filter out info for the I6 which may not apply to your car.

[80stech]

When we first diagnosed the boost terminal problem for the I6 I think it was QS who posted a really nice pick of the battery/alternator/charging it would be nice if that could be done for the V8s and both made a sticky or referenceable somehow.

I'll put out the bat signal! -- @QSilver7

[80stech]

Whoops, let me try that again! @Qsilver7

[AlpineAce]

The thing that I dont get is, wouldnt I have had the "bat" light come on before? some kind of sign? this was almost instant. even if the alternator died, should have run for a few minutes with the light on and still run normally.


Also what about the "code" what is that all about? and I dont have any code in the owner manuals.
Also why does the alarm KEEP going off? once its turned off and I turn the key, it goes off again. if I have the battery fully charged and keep it on the charger will that stop it?

[andrewwynn]

The "code" error is saying it's confused usually from loss of voltage and you need to put in an anti theft code. Check the owners manual if p o put it there.

If the car died right away after alternator quit likely the battery is also shot. You may have been running on pure alternator and no battery headroom which matches your symptoms.

Did you get the car to start/run after charging up the battery?

Check and make sure the jump point terminal bolt is tight (not 100% sure that applies to v8 but I would check in case it does)

Alarm going off often from low battery as well have you checked the voltage when this happens?

[Effduration]

A cheap cig lighter voltmeter - bought on AMZN - is great for this purpose...measures voltage when the car is off and on...

yes you can do it with a multimeter and also on the cluster submenu.

[X5only]

I once had an issue similar to yours on my 2005 4.4 - the car would suddenly die with no warning whatsoever, even on the freeway - very dangerous as the there would be total loss of power steering and breaking would be a challenge. You better get this issue addressed and avoid driving the vehicle for now. In my case, DIS diagnostics showed code "DME- 2E95 Generator - Communications loss - Fault currently present - Fault would not cause a warning Light".

I replaced the alternator, and the issue went away. I probably could have replaced just the faulty alternator component but figured for $250 for a brand-new alternator, might just replace the whole thing and not have to worry about pulley or bearing noises coming up later.