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E85 / E86 Z4 (2003-2008)
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Old 12-24-2010, 10:28 AM
z4maniac z4maniac is offline
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Location: Abu Dhabi
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Mein Auto: 2006 z4
How can I disconnect my battery? LKM problems

The light control module on my 2006 z4 3.0si has gone mad. The indicator light on the passenger side stays on even when the car is switched off. Additionally if I switch the headlights off while the car is still running and try switching them on again they wont turn on.

The indicator light will definately drain my battery. Is there a switch that I can use to just disconnect the battery? If there is no such switch should I just remove the ground connection to the battery?

Is there a way to reset the LKM? Maybe its a software problem and that will clear it ....

If I do disconnect the battery does it have any ill effects. Like maybe the car thinks I am tampering with the mileage or something?

Thanks .....
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Old 12-25-2010, 07:44 AM
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GeorgeT GeorgeT is offline
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Location: Seneca, SC
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Mein Auto: '07 750i BMW; '03 Z4 BMW
There is no disconnect switch so you'll have to disconnet the ground cable (or the positive). No, the car won't think you're tampering with the odometer - if it did, no one could change their batteries without having hugh problems when it came to trade-in/sell time (a tampered odo has an indicator that can't be removed).
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Old 12-25-2010, 10:01 AM
z4maniac z4maniac is offline
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Location: Abu Dhabi
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Mein Auto: 2006 z4
Actually what you say makes sense

I am hunting for the LKM online .... on Ebay i have found one for 200 USD. However looking at some of the posts here on bimmerfest I came to realise that the LKM goes out of its mandate of controlling the lights to actually doing a lot more. Like it keeps track of the mileage. So even if I do buy it on ebay .... how will I fit it into my z4? This will probably require some reprogramming .....

which makes me think if people are selling it on ebay there should be a way of doing this programming yourself instead of going to the stealer?
any hints are welcome ....
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Old 12-26-2010, 11:57 AM
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scottyD scottyD is offline
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Mein Auto: Z4 3.0si Coupe
You will need to code the new unit for your car which is a difficult task that you almost surely will need the dealer for. If you have access to a GT1 programmer, and someone who knows what they are doing, you may be able to get it.

Do not buy a used or new one on eBay thinking you will be able to just plug and play without some issues. You will surely get the odometer tampering dot without proper programming.

A brand new unit can only be coded - a used one cannot be recoded to a different car. The mileage stored on the unit must be less than 250 km or it will not allow coding.

I went through a lot of these issues when I added the Euro rear fog light to my US Z4, and had access to someone with a GT1 and who knew what they were doing with it since it is a dangerous tool that can really screw up your car if you don't know what you're doing.

My advice - go to your dealer or indy shop.

Also, check your turn signal lever to make sure it's in the middle since that illuminates the "puddle lights" when the car is off and the lever is moved to one side or the other. Just a thought.

And, if you have the Xenon lights, make sure you're giving them a short cool-down period (maybe 30 sec) before you try to turn them back on again. I have had similar issues but all they seem to need is a little bit to reset themselves.

Good luck.
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Old 12-26-2010, 12:08 PM
z4maniac z4maniac is offline
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Thanks a lot for the detailed reply scottyD. I am going to the dealer tomorrow. I will check with them and post a reply here.
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