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We're down to freezing temperatures in Minnesota and my car has tripped the 2B59 code. I cleared the code myself once and it came back the next morning. I was about to check codes again, but it actually cleared itself the next day (check engine turned off without intervention from me). I'm about ready to park the car for the winter and I'm undecided about replacing the thermostat sometime over the winter. Is it worth the effort to do it right away? Or, should I wait until next Spring and see if the code comes back during warm weather? Thoughts or comments?
 

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Your thermostat is sticking - the car is trying to close it to get the engine heated up, but can't and thus the code. It's like 2-3 hour diy tops, did mine last winter.
 

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Drove my car through last winter without seeing this, although just recently it's gotten very cold and I've had this code pop up a couple times. It stays away for a while, but comes back if it gets extremely cold. Although I haven't noticed any issues with the car being able to warm up, seems to come up to temp just as it always does.

Both times the code came up, it also came along with a 279D error for the electric fan motor....is this because of the ECU perhaps perceiving the inability to bring the car up to temp properly? I've never had this code before either, and it only appears alongside the thermostat code.

The first time it happened I also had 275D for an oxygen sensor but hasn't come back. Again, wondering if that was caused by a fuel mixture that might've been just a bit too rich due to incorrect engine temp, or at least was richer than the ECU would expect given what temperature it thinks the engine is.
 

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Pmalik, any online DIY instructions/videos on this?
Per TIS: google tis bmw and select your model. DIY everything
-Drain coolant: https://www.newtis.info/tisv2/a/en/e60-m5-lim/repair-manuals/11-engine/11-53-thermostat-engine-proof-coolant-lines/EMAPRjm
-Replace thermostat: https://www.newtis.info/tisv2/a/en/e60-m5-lim/repair-manuals/11-engine/11-53-thermostat-engine-proof-coolant-lines/ELrWeI9

Keep in mind these are original manufacturer repair documentation. If you are a mechanic or know a mechanic, there are almost always shortcuts for most jobs (keep that billing high!), so just keep that in mind when going through this and use your best judgement/common sense or "google" or "search/m5board", fairly easy to find most topics.

Also
M5board DIY thread (teach a man to fish): https://www.m5board.com/vbulletin/e60-m5-e61-m5-touring-discussion/201808-e60-m5-master-diy-thread.html
Link from thread - replace thermostat (WITH SHORTCUTS!!!): https://www.m5board.com/vbulletin/e60-m5-e61-m5-touring-discussion/200047-anyone-have-diy-thermostat-change.html

Cheers and GL
 

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How old is your battery? Do you experience idle fluctuations? 279D can also be related to the alternator. Did you get a reduced power check light?

Before you start the car check the battery voltage then check it after you start the engine. Let the car cold star idle drop to under 1000 then check the battery voltage again. If it's under 12v then your votage regulator or the entire alternator is goin bad. I had similar issues to you. I changed my thermostat and it didn't fix anything. It was a voltage problem.
Hope this helps.
 
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