BMW E39 5 Series Issue

[nekrum]

Hi

Guy I know has an E39 5 series and had to jump start it but initially put the battery terminals the wrong way round and ever since the car has been cutting out and going into limp mode. Apparently when running the car feels "heavy" and doesn't seem to be producing power.

He's taken it to a garage no end of times and they don't seem to know what's wrong with it. Anyone any thoughts on what it might be?!.. ecu blown, sensors etc etc?!..

Ta

[skoff]

There are a lot of electrics in a 5, I wouldn't be at all surprised if somehting important like the ECU is fried... When I was fitting my Dice Silverline I had to disconnect the battery loads of times and it always behaved a bit odd to start with when reconnected.

I would have thought a good indie, or BMW dealership could plug in their fault code reader and give him a better idea?

[gizlaroc]

Also, did you put the leads on the mount points under the bonnet??

You can not put jump straight to the battery on these cars without frying stuff.

[MarkwG]

I reckon the "fried" diagnosis could well be right: but I doubt that doing a disconnect/reconnect on the battery to reset everything would do any more damage, & it might help, so I'd give that a try first.

[sparks_E39]

gizlaroc said:

Also, did you put the leads on the mount points under the bonnet??

You can not put jump straight to the battery on these cars without frying stuff.

Really? When my battery died we jump started from the connection points on the battery, and never had a problem...

[MarkwG]

sparks_E39 said:

gizlaroc said:

You can not put jump straight to the battery on these cars without frying stuff.

Really? When my battery died we jump started from the connection points on the battery, and never had a problem...

- if you're careful you'll be OK: there is a faint risk of the explosive bolt on the +ve terminal discharging, which is a) quite nasty if you're in the vicinity, & b) bl**dy expensive to fix, which is why it's not recommended - but I've done the same & it was fine.

[Pickled Piper]

Most, if not all electrical systems on a modern car are reverse polarity protected.

Could it be that the problems are not related?

pp