Results 1 to 9 of 9

Thread: 2003 Z4 computer won't communicate

  1. #1
    Join Date
    Jul 2012
    Location
    Melbourne, FL USA
    Posts
    43
    My Cars
    2003 BMW Z4 2.5L

    2003 Z4 computer won't communicate

    An interesting problem that I can't find a solution for by searching this forum. First, the car battery was dead and since it was older I replaced it and then the battery went dead again. I had the battery charged and when I drove it next it acted like it was in transport mode since the windows wouldn't operate, the air compressor doesn't come on, etc. I just took it to a mechanic and they indicate that the car won't communicate at all. Does anyone have any ideas or can someone point me to a similar thread?

  2. #2
    Join Date
    Oct 2012
    Location
    Victoria BC Canada
    Posts
    380
    My Cars
    2004 Z4, 1700 Nomad MC
    Suspect you have alternator/regulator issue if your replacement battery had to be recharged. Fix this first and then have the car transport mode cleared by dealer/independent BMW shop.

  3. #3
    Join Date
    Jul 2012
    Location
    Melbourne, FL USA
    Posts
    43
    My Cars
    2003 BMW Z4 2.5L
    Thanks, CD. The battery draws down to the point where it won't start in 24 hours. Does it make sense that with the battery fully charged that it won't communicate? The mechanic that looked at it today is a local independent BMW shop. I brought the car home because the driver's window is partially down and I couldn't let it sit outside. I plan to take it back to them but they seemed perplexed by the inability of the car to communicate at all.

  4. #4
    Join Date
    Oct 2007
    Location
    Washington DC area
    Posts
    186
    My Cars
    Zed4
    It won't communicate to a diagnostic computer over the OBDII port? If so, there's probably a module on the communication buss shorting it out, could also explain draining the battery. You need a shop with more electronics experienced if your current shop is perplexed with the issue. Systematically disconnecting modules and fuses may help find the culprit. How much current is the car drawing when it's asleep?

  5. #5
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    I'd try a master battery reset the see the comms come back

  6. #6
    Join Date
    Jul 2012
    Location
    Melbourne, FL USA
    Posts
    43
    My Cars
    2003 BMW Z4 2.5L
    I believe by master reset you mean to disconnect the battery. The battery was disconnected for about week prior to taking it to the mechanic.

  7. #7
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    Parasitic battery drain testing:https://www.youtube.com/watch?v=QRso1A0VScw

  8. #8
    Join Date
    Jul 2012
    Location
    Melbourne, FL USA
    Posts
    43
    My Cars
    2003 BMW Z4 2.5L
    Thanks for providing another excellent DIY post. I live in an urban condo with a basement garage where the car currently sits with the battery disconnected. I really don't have many DIY options. The independent garage that laid claim to having BMW experts hasn't called me since discovering that they couldn't read the codes from the car. I'm inclined to agree with @Clearancediver that the alternator/regulator is bad and the car is in transport mode. I can't get through the logic of why that would prevent the codes to display but I am considering the strategy of having the alternator replaced and see what happens when the ECM measures +11.8v on the supply side. Wishful thinking? I'm struggling with a strategy here.
    Last edited by phlorida; 08-18-2017 at 09:21 PM.

  9. #9
    Join Date
    Oct 2007
    Location
    Washington DC area
    Posts
    186
    My Cars
    Zed4
    I would not throw parts at it "wishing" it fixes the problem. The alternator can be tested while it's in the car. What is the battery voltage with the car running when you rev it up? You just need to find a competent shop to diagnose the issue.

Similar Threads

  1. 2003 Z4 turns over but won't start.
    By Azzkicker in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 2
    Last Post: 07-13-2015, 08:22 AM
  2. Z4 E85,E86 FS: 2003 Z4 2.5i 5-Spd Sport/Prem 51.5k miles $14,000 (gauging interest)(VA)
    By Enemy in forum 3 series & Z Series
    Replies: 8
    Last Post: 07-16-2010, 11:28 AM
  3. Z4 E85,E86 Need ash tray door for 2003 Z4
    By Hermosa in forum BMW Parts Wanted
    Replies: 0
    Last Post: 06-13-2010, 01:46 AM
  4. Z4 E85,E86 2003 Z4 3.0i 6 Speed with every option Sterling Gray/Black $15,500
    By Mooseiah in forum 3 series & Z Series
    Replies: 5
    Last Post: 05-29-2010, 12:18 AM
  5. Z4 E85,E86 2003 Z4 3.0I 26000mi
    By grg600 in forum Z3,Z4,Z8 Classifieds
    Replies: 0
    Last Post: 03-20-2010, 10:17 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •