2004 545i Electrical Issues
Wondering if anyone has seen this problem and possible solution:
Car starts from cold fine. 10 minutes into the drive, Transmission Failsafe Error appears.
Turning car on and off within 1 - 2 hours does not remove error.
Turned car off for 4 - 8 hours and the problem disappears, however, 10 minutes into the drive, the Transmission Failsafe Error reappears.
Dealer wants to replace transmission, but not convinced this is some unrelated electrical isssue.
I agree it could be electrical, and you need to monitor your battery and alternator voltage real time. If the cause is electrical and it comes and goes it is very likely battery or alternator related.
Buy a cigarette lighter socket voltmeter (about $20), to monitor battery voltage before starting and during operation.
Another possibility is sticky solenoids in the valve body, but address the electrical system first.
Q: You don't mention any transmission related issues such as slamming during gear changes, so I assume the transmission seems fine other than the warning light. Can you read a code to get more specific?
A: I don't have a specific code associated with the error. There is no slamming, except at a speed that spans 3 and 4th gears. Once the error appears, the car remains in 3rd gear. It is actually intriguing as if I get to high speed before the error, the shifting is smooth and the car runs fine, but once it downshifts, it stays in 3rd.
Thank your for the voltmeter suggestion.
Transmission issues continued
Bought the voltage reader. Voltage reads low in charge mode, only 11.5 v. The voltage is fine in the charge mode with voltage reading of 14.5 v. Could low battery voltage contribute?
Not sure I follow your post.
If I read you correctly, voltage is a low 11.5V before starting but alternator is outputting 14.5 after starting?
If this is correct then battery is not holding a charge (especially if there is not a significant time between turning the car off and restarting it).
These cars are designed so that almost all systems are tied together electrically to computers and depend upon a solid 12V supply to operate accurately.
I think the first step is to go to a national auto parts chain (O'reilly, Autozone, etc.) and have your alternator, starter and battery computer analyzed for free.
If the diagnosis is that the battery is bad then replace it. Your big decision will be, do a dealer battery or buy aftermarket, and then should you pay to have the computer reset to acknowledge the new battery. My car happened to be in the shop for a replacement iDrive screen, and the battery needed to be disconnected and the computer reprogrammed anyway so the dealer quote was $289 for a new battery installed and reprogrammed. However, I have heard of $600 and $700 quotes from dealers for a new battery and programming so I would proceed carefully. A replacement of the correct size and amperage can be as little as $160 from an auto store, and the programming can always be done later. Lots of posts on this forum regarding battery replacement and correct battery model numbers.
If it is a weak battery, once the battery is replaced you can again assess the transmission and see if it cleared up.
If the battery is not the cause the next thing you can try is a trans fluid flush. Sometimes sticky solenoids can be corrected by two drain and fills. If you haven't had this done to date this is excellent preventive maintenance anyway.
Re post after assessing your battery.
How about checking the mechatronic sleeve to make sure no tranny fluid is leaking on the connector. That will do some serious damage to the electrical if the tranny fluid shorts out the wiring harness. I would start there if you suspect electrical. I know mine was replaced back in April of this year.
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