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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > 2EF4 error code: thermostat fault



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      02-11-2012, 01:25 AM   #1
queensfield
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2EF4 error code: thermostat fault

So, I got this code yesterday. I am interpreting it to mean that the thermostat is sticking. A search of this error code here reveals that the heater part of the thermostat that allows it to open slightly a bit earlier than normal is dead. That probably makes sense since I also have the "2DED code- power management standby control"- I guess the heater circuit is unable to be powered.

SES light is on. Haven't seen any overheating yet- if thermostat is dead, it is probably in open state. Should I change the thermostat? Anyone found a better way to deal with this code? Thanks.
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      02-12-2012, 12:41 PM   #2
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I had the exact same problem with my car. The code would only show up in the cold months, October to April. I cleared the code several times, but it kept coming back. The SES light comes on because the t-stat controlls the speed of engine warm up, thus controlling the cold engine start C02 emissions. If your car is out of warranty and emissions warranty then the repair is on you. If you have warranty or an emissions warranty (depends on what State you live in) then BMW should fix it for you.

The t-stat is designed to fail open, so it won't cause an overheat condition. Eventually I just changed out my t-stat and the problem went away. If your car is near 100,000 miles, you might think of replacing the water pump to. It semms most of the '06 cars lose the waterpump around 100K.
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      02-12-2012, 01:45 PM   #3
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Thank you for the explanation. Your explanation makes sense. I am out of CPO warranty, but since it is emissions related, which has 8 year warranty in CA, it might be covered. I cleared it using BT cable from a friend, and so far it hasn't come back. But it probably needs more time and a few cold starts to be sure.

I am currently at 61K miles, and am planning to change the pump and thermostat at 100K miles unless I discover any symptoms earlier- e.g. speed deviation of water pump, like you had observed and reported.
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      02-12-2012, 02:58 PM   #4
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Quote:
Originally Posted by queensfield View Post
Thank you for the explanation. Your explanation makes sense. I am out of CPO warranty, but since it is emissions related, which has 8 year warranty in CA, it might be covered. I cleared it using BT cable from a friend, and so far it hasn't come back. But it probably needs more time and a few cold starts to be sure.

I am currently at 61K miles, and am planning to change the pump and thermostat at 100K miles unless I discover any symptoms earlier- e.g. speed deviation of water pump, like you had observed and reported.
I think you can get it replaced under the CA emissions law, but double check. I think the law is specific has to what is covered (i.e. cats, fuel injection, etc.)

Good luck.
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      12-23-2013, 04:59 AM   #5
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Quote:
Originally Posted by ENINTY View Post
I had the exact same problem with my car. The code would only show up in the cold months, October to April. I cleared the code several times, but it kept coming back. The SES light comes on because the t-stat controlls the speed of engine warm up, thus controlling the cold engine start C02 emissions. If your car is out of warranty and emissions warranty then the repair is on you. If you have warranty or an emissions warranty (depends on what State you live in) then BMW should fix it for you.

The t-stat is designed to fail open, so it won't cause an overheat condition. Eventually I just changed out my t-stat and the problem went away. If your car is near 100,000 miles, you might think of replacing the water pump to. It semms most of the '06 cars lose the waterpump around 100K.
Did you replace thermostat yourself? How is it done?
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      12-23-2013, 05:52 AM   #6
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I am still sitting with an odd thermostat problem - seems to be over cooling the engine as if stuck partially or fully open. Basically the engine is typically running at 79 - 84 degrees Celsius, but does on occasions run up to 96 degrees, but almost straight away drops down again - for instance when slowing down to a stop etc. It's suppose to run pretty steady on 105 degrees as far as I know. Now the odd part is that I have no error codes, so yet again will have to just fork out more money and replace another part on this car. I did replace the temperature sensors earlier this year since it was thought that they might be giving false readings, obviously not the case.

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Originally Posted by cb224 View Post
Did you replace thermostat yourself? How is it done?
Check this thread (it's a few threads down): Pictures: Electric water pump + thermostat replace
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      02-17-2014, 11:04 PM   #7
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I just got the error yesterday driving in high 50 degree weather. I am going to try clearing the code with the JB4 interface. Interesting fact about the CA Emissions warranty. My car is Aug 2007 so I should have until 2015 but I'll research that and call the dealership.

Any other updates with you guys and the 2EF4 Map thermostat, mechanics error?
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      02-18-2014, 07:21 AM   #8
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Quote:
Originally Posted by byoung8 View Post
I just got the error yesterday driving in high 50 degree weather. I am going to try clearing the code with the JB4 interface. Interesting fact about the CA Emissions warranty. My car is Aug 2007 so I should have until 2015 but I'll research that and call the dealership.

Any other updates with you guys and the 2EF4 Map thermostat, mechanics error?
There is a heating element in the thermostat. When it fails, you get code 2EF4. Replacement of the t-stat is the only repair you can do. Eninty included replacement of the T-stat in his N52 Water pump replacement DIY.
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      03-04-2014, 05:41 PM   #9
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Quote:
Originally Posted by Efthreeoh View Post
There is a heating element in the thermostat. When it fails, you get code 2EF4. Replacement of the t-stat is the only repair you can do. Eninty included replacement of the T-stat in his N52 Water pump replacement DIY.
Can I drive around a couple weeks before replacing the thermostat? or do I need to do it immediately?
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      03-04-2014, 10:58 PM   #10
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Originally Posted by cgeorge View Post
Can I drive around a couple weeks before replacing the thermostat? or do I need to do it immediately?
You can drive around on it for as long as you want. I went around 34,000 miles between when the code first showed up and before I replaced mine. But 34,000 is about 10 months of time for me.
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      03-05-2014, 07:02 PM   #11
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thanks. I was thinking like 2 weeks or 500 miles
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      02-19-2015, 06:39 PM   #12
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Hi guys,

So I posted my thermostat DIY here, but sadly I am still sitting with the over-cooling. I am at a total loss as to why this is. Now I never had an error code to begin with, just the fact that I could see the below normal temperatures on the hidden OBD menu 7. A while back I did replace the two temperature sensors, so it was not a faulty sensor, suggesting that it could only be the thermostat then.

With the old thermostat I was typically seeing temperatures between 79 and 84 degrees Celsius, but with the new BMW OEM thermostat it seems to vary between the mid 70 degrees to the mid 80 degrees, but does sometimes climb briefly up to the upper 80 degrees or lower 90 degrees. This is all driving around town, on the open road it briefly climbs to the upper 90 degrees and then drops right down to the upper 70 degrees again.

Very strange, I have no idea what to make of it. Cannot believe that I have bought a faulty new thermostat, so has to be something else...
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