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post #1 of 3 (permalink) Old 07-31-2004, 06:21 PM Thread Starter
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Hi, I have a 97 M3 with no mods. One day the car was driving great -- except for a rattle underneath which turns out to be a problem with the Catalytic Converter -- then I let it sit for about a week and when I tried to start it--nada, battery dead. So I got a jump and took it to the dealer. While I was driving there, the check engine light came on.

The dealer said: 1.) my problem was the battery was bad and 2.) the check engine light was cause I didn't have the oil cap on tight (had recently put in a quart).

Fine. Got new battery. Dealer tightened oil cap.

Drove for a bit and check engine light came on again. Two days later: battery dead. Damn dealer. Took it to an independent mechanic. After investigating it in his garage for a week, he called and said the DME was probably bad. The idle control was staying on when the car was off, as was the DME itself, draining the battery. He said I had Oxygen Sensor problems too, due to the Cat Problem...

So now I am disconnecting the battery while not driving it contemplating either getting a new DME or selling it.

Anyone ever have a DME problem like this. Is replacing the DME the only answer? Is the O2 and the DME troubles related in any way?

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post #2 of 3 (permalink) Old 07-31-2004, 06:39 PM
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Bear is an unknown quantity at this point
Buy or borrow a ammeter and then take negative battery cable off of battery. Conncet meter (set at about 1000ma) between negative battery cable and negative batttery post and take a reading. If you see a draw of more than 100 ma leave meter hooked up and start removing and replacing fuses until the excessive draw disappears and you have isolated the culprit. I have never seen a DME affect the current draw, but who knows.
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post #3 of 3 (permalink) Old 07-31-2004, 07:09 PM
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Don't just condem the DME..DME's are VIN specific and have to be coded for your car..which can cost lots of $$$ and it may not even be the problem...there are many more modules on the vehicle that may not be going to sleep that may be draining your don't really need to do a current draw test, you already know there is a parasitic drain on the battery since it was dead...the only thing a current draw test will do for you is tell you either you do or don't have excessive current being drawn with the vehicle off...take it to the dealership and they will be able to find out which module is staying awake and why.

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