1999 E39 520i - Car losing key code won't start

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  1. 1999 E39 520i - Car losing key code won't start 
    #1
    Bimmer Fan
    Car Details
    Wonkhester's Car Details
    Model of Car:
    520i
    Year of Manufacture:
    1999
    Transmission Type:
    manual
    Car Body Type:
    saloon

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    sweden
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    Hi, I have a 1999 520i which has been perfect up until a month or so ago. I had a problem starting it, it wasnt the usual battery problem as everything worked fined but no start, no turn over, no click even. When i started to read about this problem i heard it was possible that the key lost sync with the ews and so thought the key was wrong and wouldn't start. I have had this problem a few times now and when i turn off the key, wait a few seconds and try agian, after maybe 10 attempts it sometimes works ( one time not until i got out, locked it, unlocked it again and then tried it). Is there anyone who can give me some thing i can try to identify for sure where the problem lies, I know if i take it into bmw here in sweden its going to cost the earth just for a diagnostics check. Is there a diagnostics tool i can buy that i can use myself which reads these electronics fault codes maybe? Very frustrating to be stuck in the middle of nowhere with small kids in the car.
    Any ideas very welcome.
    thanks
     
     

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    #2
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    Tried the spare key?
     
     

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    #3
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    Wonkhester's Car Details
    Model of Car:
    520i
    Year of Manufacture:
    1999
    Transmission Type:
    manual
    Car Body Type:
    saloon

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    Yes, does exactly thesame with that. Thought that it might be something to do with the battery at first but then i read that with this model there is no battery in the key connecting to the start system. I am just hopeful that someone knows if there is an alternative than taking it to a dealer to find out they want to change the ews for £1500
     
     

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    If both transponders are not communicating, then I fear a code mismatch between the EWS and ECU . Looks like a trip to the dealer or specialist
     
     

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    #5
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    Wonkhester's Car Details
    Model of Car:
    520i
    Year of Manufacture:
    1999
    Transmission Type:
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    Car Body Type:
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    If its a code mismatch problem, is it usually something that is reprogrammed or is it a case of change the ews, or even both ews/ecu?
    cheers
     
     

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    Not sure if the transponder can be reprogrammed, but a new EWS can. Will also need to set up the rolling code table from the EWS to the ECU.
     
     

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    #7
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    Wonkhester's Car Details
    Model of Car:
    520i
    Year of Manufacture:
    1999
    Transmission Type:
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    Car Body Type:
    saloon

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    Not got anywhere with this problem yet so thought i would ask one more time before putting my faith in the dealer. I sat in the car park today turning the key on and off about 30 times, 10 seconds between each turn, and then it started. After that it started ok again a few times. Its a matter of time till the key goes out of sync again, i just wondered if anybody can shed some light on why this might happen so infrequently, which component(s) are most likely to be causing the fault and what alternatives do i have for repair? Any tests, ideas welcome.
     
     

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    #8
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    GT53's Car Details
    Model of Car:
    520i, 528i
    Year of Manufacture:
    1995, 1998
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    Manual, Automatic
    Car Body Type:
    Saloon, Touring

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    I've recently had the same problem. Obviously diagnosis of an intermittant problem can be difficult as the car may start working correctly while you are testing. However, there are two simple tests to check if the key is being recognized.

    1. A valid key will unlock the doors if they are deadlocked when you try to start the car. To test-

    - Wind the drivers window down
    - from outside the car, use the key to deadlock the doors
    - reach into the car and try to unlock them from the inside (to confirm they really are deadlocked)
    - place key in ignition switch and try to start car, if the key is recognized the doors will unlock (obviously if the car starts then you haven't proved anything, only if the starter motor fails to turn but the doors unlock will it confirm the key/EWS is OK and the problem lies elsewhere).

    2. If the car is a manual, as long as the key is recognized you should be able to bump start the car. Obviously for this test you need to try the key in the ignition until the starter motor doesn't work, then without turning the ignition off try and bump start the car. If it starts then the key is being recognized.

    These two tests only confirm if the key is being recognized. If they fail, it does not necessarily mean the key is not being recognized, the fault may still lie eleswhere.


    There are a number of reasons the starter motor will not turn even if the key is being recognized, these include:

    Clutch Switch fauty (manual)
    Gear stick position reported incorrectly (automatic)
    Alarm faulty (believes it is still activated)
    Onboard computer faulty
    Door locks report doors deadlocked when they are not
    Starter motor immobiliser relay (inside EWS) faulty
    Starter motor relay (on starter motor) faulty
    Starter motor faulty
    Ignition switch faulty


    Try the key recognition tests first and report back how you get on. Some of the other faults can be tested with a multimeter on the EWS connection plug. If the key checks out OK then I will try to provide some simple multimeter test.
     
     

  11.  
    #9
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    Wonkhester's Car Details
    Model of Car:
    520i
    Year of Manufacture:
    1999
    Transmission Type:
    manual
    Car Body Type:
    saloon

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    Thank you very much for your detailed reply. I have a manual gearbox so will have to wait till next time this fault re occurs until i can try to bump start it. However, i do have a Fault code engine diagnostic tool i can plug in to the OBD socket. I haven't tried this yet as i wasn't sure the tool would read electonic faults. Is it worth a try do you think? The other fault possibilities sound interesting! I never knew there was a clutch switch. How does that operate? I will do the first two tests as you descibed and come back to you.
    Thanks again
    robin
     
     

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    #10
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    GT53's Car Details
    Model of Car:
    520i, 528i
    Year of Manufacture:
    1995, 1998
    Transmission Type:
    Manual, Automatic
    Car Body Type:
    Saloon, Touring

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    The clutch switch should send a signal to the immobilizer, only allowing the starter motor to turn if the clutch pedal is depressed when you turn the key.

    As far as the fault code tool goes, I believe the OBD socket on pre September 2000 cars only provides diagnostic information relating to the Engine Management Unit (DME) and Automatic Gearboxes (AGS and EGS). All other diagnostics are performed from the round 20 pin connector in the engine bay. However it's still worth using it just to see if any faults are recorded on the DME. Please be aware that some faults can be recorded purely from disconnecting the battery or other items while you are working on the car so it's always best to write them down, reset the module and then see if they come back after a drive.
     
     

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