[Sabao767]

I replaced my water pump and thermostat on my N51, everything works but I keep getting this code. After I clear the code I can drive for as long as I want to, when I turn the car back on it comes back.

Did I get a bad thermostat or is there something else wrong?

These are the readings I pulled with the Carly app

[Phyrexia]

Indicates an open thermostat, ie a thermostat that has failed.

[Phyrexia]

Your coolant is taking too long to get to temp. Note the temperatures in your freeze frames. I think the target for coolant temp is 100°C

[Sabao767]

Originally Posted by Phyrexia

Indicates an open thermostat, ie a thermostat that has failed.

I replaced the thermostat again and am still getting the same 2EF5 code. Any idea what else could be causing this? Would the temperature sensor cause this issue? All the connections are good on the thermostat and the water pump. These are the latest readings[IMG][/IMG]

[Destructo09]

I know this is an ancient post but it's one of the top forum posts that comes up when I google this issue and I discovered the reason for my problem. I had symptoms of a stuck open thermostat, this code and replaced the thermostat and it didn't solve my problem just like this person.

At the suggestion of some other posts I changed out the coolant temp sensor with a VNE sensor from FCPEuro even though my original BMW one from 2007 was testing good and seemed to report correct values. This had no effect on the issue and the DME was still commanding the thermostat open and temps would only get to 50-60C on the road.

I knew my A/C system had no refrigerant in it due to a condenser with some road debris damage but being winter I was holding off fixing it until I really needed A/C again. I found one post that possibly suggested the low pressure switch for the A/C could be a potential cause. Tonight I decided to disconnect the compressor wiring and the pressure sensor on the high pressure side (I think, passenger side behind the heat shield). I did this after confirming the new coolant temp sensor didn't make a difference and voila, soon as the pressure switch was disconnected which I believe makes the circuit open again the DME allowed the thermostat to operate like it should and the coolant got to full temp and the water pump increased speed as normal and the radiator fan ran at a lower speed like expected as needed. The temperature stayed in the 95C after I disconnected that.

TL;DR: Apparently the A/C pressure switch being closed due to low pressure will cause the DME to prematurely heat the thermostat so it opens early and cause the stuck open thermostat symptoms a lot of people have seen.

[stylesp]

Originally Posted by Destructo09

I know this is an ancient post but it's one of the top forum posts that comes up when I google this issue and I discovered the reason for my problem. I had symptoms of a stuck open thermostat, this code and replaced the thermostat and it didn't solve my problem just like this person.

At the suggestion of some other posts I changed out the coolant temp sensor with a VNE sensor from FCPEuro even though my original BMW one from 2007 was testing good and seemed to report correct values. This had no effect on the issue and the DME was still commanding the thermostat open and temps would only get to 50-60C on the road.

I knew my A/C system had no refrigerant in it due to a condenser with some road debris damage but being winter I was holding off fixing it until I really needed A/C again. I found one post that possibly suggested the low pressure switch for the A/C could be a potential cause. Tonight I decided to disconnect the compressor wiring and the pressure sensor on the high pressure side (I think, passenger side behind the heat shield). I did this after confirming the new coolant temp sensor didn't make a difference and voila, soon as the pressure switch was disconnected which I believe makes the circuit open again the DME allowed the thermostat to operate like it should and the coolant got to full temp and the water pump increased speed as normal and the radiator fan ran at a lower speed like expected as needed. The temperature stayed in the 95C after I disconnected that.

TL;DR: Apparently the A/C pressure switch being closed due to low pressure will cause [...]

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