Very oddly the battery failed yesterday on my 540i with OBC2.

Have had no previous problems etc? when the engine tried to start all sort of manner of things lit up on the dash board, one of which was "engine protection mode" or somthing to that effect. also there was a strange noise from either engine area or behind the dasboard?  as was late for work had to jump in my other car and leave it.

Assume the battery is flat, having a look later today,

Question  1)  should I jump start it ?

Question2)   Should I recharge it on the car?

Question 3) Replace battery?

All of which begs the question, will a reset or recode be needed on anything engine ecu cd player etc if the battery is removed? BMW or DIY reset?

There is enough life to run the interior light and dash lights radio etc but not the starter ( heavier load)

Any help or advise gratefully accepted.

Jeff TT

Jeff

Did the engine actually turn over?  If it didn't, it could well be a duff battery.

If it is a duff battery.......

In my experience batteries just go without notice.  Drive home one night, out the next morning and nowt.  Jump start in the car following the correct procedure in the manual (was also discussed on this forum http://www.bmwcarclubforum.co.uk/forum_posts.asp?TID=11822&PN=3 - http://www.bmwcarclubforum.co.uk/forum_posts.asp?TID=11822&a mp;PN=3  )  Best to get a new battery rather than try and charge up a duff one as it will always go flat again.  Main $tealer battery for mine is approx £50.

How old is the battery, they normally last about 4-5 years?  Replacing the battery on my last car seemed to cure all sorts of electrical gremlins.

Was the strange noise you heard a clicking?  If so this will have been the starter solenoid clicking in and out.  There will have been enough power to energise the solenoid and make it click in and out but not enough to crank over the V8.

I have been told that removing a E39 battery will not wipe the radio code, there is no code for E39s apparently.  My battery was disconnected when the tranny was being worked on and all I lost was the trip mileage and the clock.

If the engine did turn over and then made the strange noises and then went into limp mode it could be anything. 

Turn on the ignition but don't start it, just to make sure all the lights and test sequences work and then go out.  If all lights are out, pray then start her up.

Hope this is of some help.

Andrew

Jeff

Just a thought, but if you were getting all the lights on the dash and not turning over, but a clicking or whirring noise, then it could possibly be the starter motor.  The solenoid, as Andrew pointed out, will make a click (single or continuous, depending on which bit is duff).  It would seem plausible that the car might try to "protect" itself if it detected an issue.