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Discussion Starter #1 (Edited)
Hi everybody,

First want to say what a fantastic resource of information this forum is to less mechanically inclined folks like myself. People are always helping each other out and rectifying solutions to issues.


Anyways...the not so fun part.

I've been driving my 2002 525i for over a year now as my every day (and only) vehicle. 44,000 total lifetime miles. A week ago I got the dreaded "trifecta" of yellow BRAKE, ABS and Triangle warning lights on my screen. Figured I probably needed a new wheel sensor or something so I didn't rush to go out and get it fixed. A few days after these lights being on, I was doing my daily commute home in 40mph and the "trans. failsaife prog." lights up and my car goes into 1st gear and I lose my power steering (WTF?). Was able to pull off the side of the road, recycle the ignition and the trans prog warning went away and my transmission operated normally.

I took it into the shop to get the code read and it indicated it needed a rear sensor replaced (did not specify which one) and a steering wheel sensor. Total cost for all was over $1000 so I ordered 2 wheel sensors from BMW instead. I replaced the right rear sensor yesterday and to my excitement the trifecta of warning lights went away for an entire day of driving the car. However...today the trifecta of lights returned and when I was commuting home, "trans. failsafe prog" came back on, 1st gear and no power steering. So frustrating.

I know this topic has been broached so many times on this forum but I have not been able to find a thread where it mentions loss of the power steering from the "trans failsafe prog." each time this has happened there has not been any traffic so it's not a big deal but if this were to happen in traffic, the car is basically unsteerable until recycling the ignition. I'm going to replace the other rear sensor on the other wheel as well and see if that does anything.

I guess my question is, why is the power steering going out upon receiving the trans failsafe prog message? The car sits (unfortunately) in 100+ degree heat for 4-5 hours daily. The trifecta of lights come on intermittently. I have noticed though that when it has sat in the garage overnight and not left out in the sun for extended periods, the warning lights tend to be off. When the car is hot the lights are always on. I don't know how heat would be affecting this but there seems to be a correlation. I checked the battery also and it was surprisingly low at only 51% of a charge. The auto shop said they "checked it" and it was fine but that doesn't seem like an acceptable voltage.

I have also done the code 21 and code 2 reset on the computer on the screen.

Thank you so much for the help.
Cheers
 

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How did you determine 51% charge? A defective battery can cause electrical gremlins to surface.

This reading implies a battery voltage circa 12.25 V. A healthy, fully-charged battery measures 12.6 V

How old is the battery? Note that high temps are harder on batteries than low temps.
 

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Wingnut
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battery/charging issues can lead to the trifecta and trans failsafe indications. the actual voltage at the battery would tell us a lot more.
 

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Discussion Starter #4 (Edited)
Hi guys,

thank you for the help! I attached a charger directly to the terminals on the battery itself and my readout gave me a 51% charged indication, and it slowly took a charge but I didn't not leave it on very long. The battery sticker date code is H4 (2014?). The little clear window on the battery that indicates if it is still good is the color green.

I went today to the BMW dealership and got a new battery. They also reconfirmed that the warning trifecta can be caused by a faulty battery. I hooked the new battery up to my charger and low and behold: 45% Not sure if it just didn't have a charge on it already...but guessing my charger is crap.

I realize the volts will vary depending on if the car is running or turned off.
 

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Never seen the power steering issue due to a bad ABS wheel speed sensor.
Have you inspected the 2 front WSS?
Look bad wire insulation and/or cracking harness.
Just as a reminder Only use OEM ABS WSS as you may have read aftermarket sensor don't work if they do they fail very soon after installation.
 

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Wingnut
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charged battery =12.6 volts. alternator output engine running fast idle *depending on load etc* should be 13.8 to 14.2 volts.hows the results with the new battery?
 
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