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Thread: Battery Drain/no start, 03 745Li

  1. #1
    Join Date
    Oct 2014
    Location
    Trois-Rivieres, Quebec, C
    Posts
    3
    My Cars
    2003 BMW 745LI

    Angry Battery Drain/no start, 03 745Li

    1st post! I'm a Canadian 7er owner, love to drive it! I bought new battery on 11/2014 (Trans-Canada Gold) and had it registered and everything was fine. Car sits outside from Sunday to Thursday every week. I had to jump start the car 2-3 times during winter of 2014-15 (when temperature gets crazy low). From last December to January had to jump start it at least 10 times. Got tired of messing with it and had the battery changed by warranty. Registered the new battery and since then IT'S A COMPLETE MESS! Drains, no start, had to boost it, etc. Charged it for 54 straight hours and battery wasn't even full. Got it to the battery shop, they runned test on my it, fully charged it and said battery was ok. Put the battery back in the car, went golfing and, guess what, 5hours later car won't start (had to jump start it with a golfcart smh). I realised that when I park my car, it goes to sleep, then it awakens and the "Parking Brake Fault" lights comes on the dash (without having the car unlocked or whatever). Looked thru MANY different threads about this type of problems. At once it was pointed out that the Parking Brake module is known to break since gears are plastics inside. opend it, everything is fine!

    https://www.hostingpics.net/viewer.php?id=425218image1.jpg

    Some other guys pointed out to the IVM module tends to get corrosion on the solder and cracks.
    Changed the IVM module on Thursday, still no start. So I jump started it. Engine has never been running so smoothly, gears shift better too. Although I lost my under seat woofers . Drove to battery shop, battery was matter of fact drained, bought a new charger (old one was switching on and off all the time). Came back home charged it, once fully charged, try to get it started won't start. Unplugged and plugged back the loop jumper in the glove box compartment to reset the MOST bus (saw on a forum that my no start/woofer problems may have been cause by this). No start. Plugged battery charger this morning, battery was totally drained! I'm REEAAALLLYYYY starting to get furious at it!
    Mechatronic seal problem? Tranny problem? CAS alignement problem (code 2737)? SBSR problem? Fuel pump problem? Comfort Acces problem? Crank position sensor problem? Starter problem?

  2. #2
    Join Date
    May 2017
    Location
    USA
    Posts
    159
    My Cars
    E90, E46
    A lot of the things you mentioned won't cause a no start.
    you likely have a battery draw but you need to confirm it with a draw test. It could also be an Alternator not charging which is common on higher mileage E65s.
    AFTER you verify you have a good alternator and you still need answers...
    get yourself a multimeter that measures up to 10amp DC.
    hook your red lead on your meter to a GOOD ground. Loosen your negative battery terminal and hook up the black meter lead to the negative post BUT try not to pull off the battery cable from the post until you are able to clip the meter lead to the post. It can be tricky but you want the battery cable AND the meter lead both touching the post at the same time. Once you have a good connection with the meter go ahead and remove the battery cable.
    So your meter should be 1 lead on a good ground and 1 lead on the negative post of the battery.
    You should have a reading on your meter now.
    let the car sit there for atleast 20 minutes and you should not have a reading of more than .040 amps ( 40 milliamps ).
    Do NOT mess with the positive terminal or cable in any way and definately DO NOT hook your meter up to the positive cable in any way. You do not need to mess with the positive post or cable and in fact put a rag over it so your not tempted to mess with it or bump it.

  3. #3
    Join Date
    Oct 2014
    Location
    Trois-Rivieres, Quebec, C
    Posts
    3
    My Cars
    2003 BMW 745LI
    Quote Originally Posted by SlackTube View Post
    A lot of the things you mentioned won't cause a no start.
    you likely have a battery draw but you need to confirm it with a draw test. It could also be an Alternator not charging which is common on higher mileage E65s.
    AFTER you verify you have a good alternator and you still need answers...
    get yourself a multimeter that measures up to 10amp DC.
    hook your red lead on your meter to a GOOD ground. Loosen your negative battery terminal and hook up the black meter lead to the negative post BUT try not to pull off the battery cable from the post until you are able to clip the meter lead to the post. It can be tricky but you want the battery cable AND the meter lead both touching the post at the same time. Once you have a good connection with the meter go ahead and remove the battery cable.
    So your meter should be 1 lead on a good ground and 1 lead on the negative post of the battery.
    You should have a reading on your meter now.
    let the car sit there for atleast 20 minutes and you should not have a reading of more than .040 amps ( 40 milliamps ).
    Do NOT mess with the positive terminal or cable in any way and definately DO NOT hook your meter up to the positive cable in any way. You do not need to mess with the positive post or cable and in fact put a rag over it so your not tempted to mess with it or bump it.
    Alternator was checked by the battery shop and was ok. And since the drawn happened overnight after I had the battery fully charged without driving it, I ruled this out. Once I'll have the multimeter connected and realise there is a module staying awake, I'l' try disconnecting them one at a time to see which one is draining the battery. Which one I should check first? Thx

  4. #4
    Join Date
    May 2017
    Location
    USA
    Posts
    159
    My Cars
    E90, E46
    The vehicle does stay awake for a while after you shut the key off which is normal. You cannot take the reading seriously until atleast 20 minutes have passed...
    the first things to unplug is TCU, NAV, AMP, SDARS. Fortunately they are all left hand trunk.
    after that diagnosis becomes quite a bit more complicated.

  5. #5
    Join Date
    Oct 2014
    Location
    Trois-Rivieres, Quebec, C
    Posts
    3
    My Cars
    2003 BMW 745LI
    Quote Originally Posted by SlackTube View Post
    The vehicle does stay awake for a while after you shut the key off which is normal. You cannot take the reading seriously until atleast 20 minutes have passed...
    the first things to unplug is TCU, NAV, AMP, SDARS. Fortunately they are all left hand trunk.
    after that diagnosis becomes quite a bit more complicated.
    Last time I parked the car and locked it I let it stand for 45min and when I came out to see if it was in sleep mode it was (seats lights were off). Then all of a sudden the Parling Brake Fault came on the cluster, and I overheard the NAV dvd player loading the disc. I assume to give the car the impression that trunk is closed I'll have to manually close latch to let it go to sleep mode. I'll do the diagnosis thursday when I'll get back home.

  6. #6
    Join Date
    Feb 2017
    Location
    Georgia
    Posts
    6
    My Cars
    BMW E66 745Li
    new battery is start/stop battery? when i bought new standart 110Amp battery simptoms was some. then i bought AGM start/stop 95Amp battery and problem was solved.

  7. #7
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    The car sits to much have a shop do an energy diagnostic test and test for draw. Also there is the battery switch on the passenger side trunk area at the very top of the electrical junction panel that when on shuts off certain electrical items so the battery wound drain so quickly when the car is parked for extended time. and but a battery tender on your car.

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