Hi guy's
This is my 1st thread and a bit embarrassing at that ,but the best thing is it was my brothers fault
I lent him my cooper s 55 plate for a few weeks while he was looking for a new car ,
He returned it to me today to tell me that he left the lights on and the battery went flat ,so he took it off and charged it over night to bring it back to me today, now here is the problem
When he put the battery back in the car he put the red live wire to the neg (black side of the battery and the black wire to the pos side + and didn't realise it for a few seconds before he looked at it again to see he looked at one of the top up plugs had a cross on it
Now when you turn the ignition on and start the engine all the dash light's stay on i.e air bag engine fault light oil every thing
Is there a way of reseting the ECU or is this a bmw thing and does anyone have any ideas if there could be any damage caused by this
it all starts OK and seems to run OK ,,,Thanks guy's and a bit of info would be good
Oh dear !!
Yes it looks like damage has been caused to at least one of the computer units.
My Best Advice in your particular situation ....
Delete this thread {just in case someones watching} & then take your car back to the dealer denying all knowledge of whats gone on, & ask that they put it right.
Could be expensive otherwise
First, are you sure that the battery is not dead? It is possible that he may have fried it. I would buy a new one first and make sure you install it correctly. If that still doesn't work, it is possible that he damaged one of the computers. If that is the case, it may be a costly repair, one that your brother should be paying for.
If it starts and runs as per normal, then you have probably been lucky. Sounds like the main OBC and BC1 control units are intact. If you are really lucky, you might only need the dealer to read out the fault codes and reset the OBC.
However, I would be very surprised if the rectifier pack in the alternator has survived. So you would be wise to get that checked out.
As already suggested, the battery might have suffered, but it doesn't sound like any major fuses have blown, so maybe not. It would be wise to have the battery checked though.
Your brother was lucky he didn't set the airbags off!!! Modern systems don't like been disconnected from their power supply and when reconnected surges of power do interesting things...
Well I wouldn't worry too much. One way of resetting the main OBC, is to disconnect the battery, wait 30 minutes and then reconnect it. I've done it several times. So have others on MINI2. No reports of airbags deploying.........yet.
I have a s2000 as well and the way to reset the ECU on that is to disconnect the battery, I'll try a new battery on it on Wednesday fingers X crossed and hopefully things will be okay, Thanks again and I'll keep you posted
Save yourself the Money ...Its NOT the Battery, {I`m an Vehicle Electrician amongst other things}, & if there was any problem with the Battery then it wouldnt have the power to start the car, & once running a low battery just wouldnt be able to influence all the dash lights to remain on !!
It could be a host of other things from faulty ECU or Alternator as others have suggested, or something just may need resetting by BMW, but its definately NOT the Battery in this particular case.
This probably isn't of much use - but I remember reading somewhere (perhaps in a Mini brochure?) that the electrical system is 'smart' enough on our cars to detect when a battery is hooked up incorrectly. The horn is supposed to honk or something like that to 'alert' the person doing the work that something isn't right.
Anyone else remember seeing something about this feature? Perhaps it was a US thing?
The Suby we have (2004) will not allow damage to occur if it is hooked up incorrectly. I cant imagine that MINI would not have a simple circuit in place to protect the system.
If everything runs then I think its a simple reset of the lights. beemer will charge you but probably only £30-£60 basically 1/2 hours work. If it was anything major the car would either not start and run, or would be in take me home 20mph mode. if all works fine and just lights are on then its just a dealer reset thats needed (the airbag does not reset with the normal battery disconnect method)
This is the most unprofessional bit of site management I have seen since I was banned from a certain other site...at least they had the excuse that they were enthusiasts who had strong views and not professionals paid to keep thier cool!
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battery wrong way round , HELP 
