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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E46 (1999 - 2006)

E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 02-13-2013, 01:06 PM
Bear77 Bear77 is online now
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Location: East Bay
 
Join Date: Oct 2012
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Mein Auto: '04 325iT
Alternator Failure After O2 Sensor Replacement

What are the odds of this? I had my wagon on the shop to replace the post-cat O2 sensors yesterday. I picked the car up upon complestion and a few miles down the road, the SES light came back on. Another 20 miles or so down the road, the battery light came on, then the car went into limp mode. I pulled over, turned the car off, and started back up with no problems.

Today, I'm driving to work and about 30 miles into my 40 mile commute, I start experiencing the same problems, but this time the gauge needles get stuck and the car dies.

I get towed to the same shop I had the O2 sensors done (indy shop with great reputation and great service with them in the past) and they report a failed alternator. This seems to line up with the symptoms I described, but I'm stymied at how this didn't come up when the car was in the shop yesterday. Do alternators fail so suddenly? Thoughts?
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  #2  
Old 02-13-2013, 01:14 PM
JKRIT JKRIT is offline
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Alternators can fail suddenly, unpredictably. I am more curious why you were having post-cat O2 sensors replaced. They almost never need replacing; It's the pre-cat ones that actually work to monitor exhaust and control fuel mixture.
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Old 02-13-2013, 01:17 PM
Bear77 Bear77 is online now
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This all started with a SES light. Codes showed faulty post-cat O2 sensors.
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Old 02-13-2013, 02:25 PM
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smolck smolck is offline
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Location: Birmingham, AL
 
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Mein Auto: 2004 ZHP Sedan
Yep, likely a major coincidence. But I don't trust any man other than myself to work on my car so it is hard for me to say they didn't mess with it. Who knows?
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