AudiGirl73

I was unfortunate enough to be rear ended the other day. Other vehicle hit me hard. I'm assuming the seat belt tensioners went off because I had white smoke coming out of the vents and looked like also my hood. There was so much of it I had to open up the sunroof. My battery also disconnected so my car would no longer start. I still had auxiliary power. Car had to be towed. The damage looks to be contained to the rear end, visibly, bumper, muffler, trunk. If it wasn't for the battery disconnect, theoretically it seems like I would have been able to drive it out of traffic and onto the shoulder.

Few days later, I put the key in, no response, no dome lights, no hazards, nothing but this weird warning light combo remains even though the key has been removed (it's a United States, 2012 that does not have the keyless option). Besides these warning lights, everything in the car is dead. Does anyone have any idea what this means? I know what each symbol stands for, and all make sense with the force of impact I experienced, but what type of damage could make my car completely lifeless? I love this car, and I hate seeing it in this sad state. I hope it is something that can be repaired.

Note to anyone considering a S/Q5, get one. This has been my favorite vehicle I've ever owned. It drives like a car, not a truck, and is great on wet roads and in snow.

waninae39

bmw have a explosive cutter that disconnects the battery in an accident.
i think that the q5 has something similar.

the battery is under the spare wheel

thus i think that the main battery has disconnected.

Bob Petruska

Yes there is an explosive battery disconnect on the Q5 when in an impact accident. Dealers usually don't stock them as for local regulations pertaining to storing explosive devices.

I assume that the explosive disconnect removes most "main" power as the OP stated he still had some residual powered up items.

The Power Management system will also shut down individual electrical sections of the Q5 if the battery can't supply enough energy.

Best thing to do if get a new explosive battery disconnect, if it indeed fired (check it), charge up the battery, and work from there.

If for some reason you need a new battery you should read the battery post below on this page.

Redd

IIRC the "pyrotechnic fuse" or whatever they prefer to call it, consists of a special fuse on the ground bus. If the airbags or belt tensioners trigger, a pulse of electricity is also delivered on a dedicated circuit to this pyro, causing it to either blow like a fuse, or a pyrotechnic. Which is unclear, but either way the effect is the same.

When I was looking into this spijun kindly posted some references. Apparently it blows a link which cuts the battery off from the alternator and starter, but allows the auxiliary circuits to still drain battery power.

This ensures that you cannot drive a car that might be unsafe, but you can open the doors to escape (which should also unlock automatically), open the windows, sound the horn and headlights to get help, etc.

Pretty damned foolish unless you assume the driver is an idiot. The situation can be remedied by replacing that pyro with one of the conventional "stamped sheet metal" large fuses that Audi uses directly by the positive terminal of the battery. Or a piece cut from a soda can.(G)

If I could make any sense of the circuit drawings, I'd just UNPLUG that pyro, to make sure it wouldn't be an issue. But I don't like fooling with pyros when I can't quite be sure where or which they are. The diagrams don't bear any resemblance to the wiring by my battery.

Maybe next time I'm in to the dealer, I'll ask someone which wire that is.

Bob Petruska

It's officially called a Battery Interrupt Igniter..........


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rdA4WtQ5

When the car's air bag, seat belt tensioners or battery disconnect is fired there are modules that need to be replaced. Once the spent module's tensioners, air bags and battery disconnect are replaced the car has to visit the dealer by flat bed if serviced yourself and be plugged in and connected to the fatherland so that your car can be a car again. Until that process is done your car will not start. Most if not all body shops deal with this almost every day and for all manufacturers.

Redd

Thanks, Bob, I hadn't seen those drawings before. Interesting how they simply don't mention the wiring. The last set I'd seen actually referenced one of the connectors as being the one carrying the "Blow!" signal, but didn't make it clear which one that was. These drawings seem to indicate there is one connector running aft and another running down, and unplugging the right one *should* simply disable the fuse blowing.
Although, perhaps if the ECU senses the fuse has not blown on signal, it calls out a Hessian Guard to chastise and admonish the driver instead?
As rd points out, there can be many valid reasons and many systems in need to attention after an impact. However. There are also many reasons why disabling the car may actually prove dangerous.
A pothole on the Cross Bronx Expressway could trigger them, leaving the driver in a dead car, in the middle of dense traffic, unable to drive it to the shoulder. Or, some yoyo tossing bowling ***** off overpasses (it happens) could leave one occupant injured, nd the driver unable to take them to safety. Same same, when there's a rockfall in Colorado or BC and a car is struck, struck hard, and the driver may need to get to medical aid, urgently, and need their own vehicle to be running to do it.
Common problem? No, but a decision for the driver--not the car maker. Especially when it is done without the driver's prior knowledge and informed consent. And without even putting in a "reset" or bypass mode.
While I have my car in for the "auxiliary heater reprogramming" I think I'll ask them to show me which lead that is. So I can regularly inspect it and make sure it is properly connected and in good working order, of course.(G)

Bob Petruska

I have to look deeper into this as there is the battery Energy sensor (coulomb counter) that furnishes the Power Management system with the battery, charge/discharge data, open circuit voltage, etc. that is connected at the battery. The igniter module could be part of this. Audi engineering never fails to impress me...........(G)!

Redd

I think the coulomb counter is technically software running on the ECU, which depends on a conventional shunt in that assembly for data. One good location for both, but separate plugs. Shunt wires don't like sharing.

Ages ago a friend of mine had a Fox wagon. Nice car. And one night calls me "I'm about 1/2 mile from home, the car won't run". It turns out that the alternator had blown (requiring a then un-heard-of huge metric socket to access) and the exotic fuel injection system was counting pulses from the alternator to determine engine speed. So, no alternator output? Then we must be parked, shut the fuel supply and turn the engine off.

Yeah...Audi has never considered "limp home mode" to be a useful option. What the hell, you can always call the dealer, 24x7, and they'll bring you a new one, right?

I foolishly thought the corporate mindset might have grown a little since then. My bad.

AudiGirl73

Thank you all! I was hoping it was part of the battery disconnect, and not something more serious. I agree Audi should look into a limp home mode. I was a sitting duck on a busy street after being rear ended during rush hour. But at least it gave me enough power while I was at the scene of the accident. I wrongly assumed that the level of power would remain the same. Once everything is fixed (hopefully sooner than later) I will update with more photos, what ended up being wrong, and approx costs of the fender bender.