OBD code 0740 on 1997 740iL - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 11-04-2009, 02:39 PM
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Cool OBD code 0740 on 1997 740iL

checked the code and cleared it, the transmission works fine, but the code seems to appear back up when I turned the headlights on at night, seems like the alternator or voltage regulator may start going out, I can see the haedlights flickering every now and then, some how I heard about the voltage regulator having something to do with the transmission ( apples and oranges )
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#2 (permalink) Old 11-05-2009, 02:58 AM
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Could be the alternator on its way out as the code is defiantly a transmission code , if the voltage is not stable it will affect the transmission solenoids especially the torque converter pressure regulator and throw up codes, Ive heard of boxes going in to TRANSFAILPROG just due to the battery being to old and not holding the voltage, as your lights are flickering its either the Alt or Batt or could even be both as the Alt hasn't been charging the batt,so the batt has had massive drains on it to keep the car going.

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#3 (permalink) Old 11-05-2009, 08:11 AM
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I now the battery looks brand new, ( not necessarily my prefered brand ), I'll check the alternator output this weekend to see if in fact the alternator is the culprit, thx
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#4 (permalink) Old 11-05-2009, 09:43 AM
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The trouble with alternator tests is they dont test them under load or at say 4000rpm at tick over it maybe fine, so to test it you need to be in 'D' with the foot and hand brake applied up to 4000rpm and test it at all rpm ranges, I had one that only started to fail at 2500rpm at idle it was perfect.

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