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Discussion Starter #1 (Edited)
Hello,

I have a 2014 328i x Drive, 60K miles. Every since it started getting cold in New England (under 30 degrees) my check engine light has come on with code "U1408". The shop I usually go to thought it was thermostat related issues and it should be under warranty. So, I brought it to the dealer and they replaced the thermostat under warranty, but the same day it was around 15 degrees out and the CEL came back on, this time with U1408 and P0128 (low coolant temp). I brought it back to the dealer, but it was around 50 degrees that day and of course the light was no longer on :rolleyes: . They didnt see any fault history related to the thermostat.

The CEL comes on with U1408 whenever it is cold out (under 30 degrees) and will turn off on warmer days. The oil temperature gauge also doesn't move above 160 when the light is on, and the fans run super loud when its cold out and I have the heat on. Does anyone know what this could be? Car still drives ok, don't seem to be experiencing any power limiting.

Thanks!
 

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Discussion Starter #2 (Edited)
So I accessed the hidden menu in the cluster and after a 30 minute drive (mostly highway at 65mph) the oil temp and coolant temp were only around 90 degrees C (194 F). It was 40 degrees F outside. This seems to be below operating temperature and almost sounds like the thermostat is stuck open, even though it was just replaced. The CEL also shut off again. The oil temp gauge does match what the car is telling me. Any thoughts?
 

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Hello,
I***8217;ve the same problem as you had with oil temperature. Can you tell me how did you fix it?

Thank you
 

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Hello,

I have a 2014 328i x Drive, 60K miles. Every since it started getting cold in New England (under 30 degrees) my check engine light has come on with code "U1408". The shop I usually go to thought it was thermostat related issues and it should be under warranty. So, I brought it to the dealer and they replaced the thermostat under warranty, but the same day it was around 15 degrees out and the CEL came back on, this time with U1408 and P0128 (low coolant temp). I brought it back to the dealer, but it was around 50 degrees that day and of course the light was no longer on :rolleyes: . They didnt see any fault history related to the thermostat.

The CEL comes on with U1408 whenever it is cold out (under 30 degrees) and will turn off on warmer days. The oil temperature gauge also doesn't move above 160 when the light is on, and the fans run super loud when its cold out and I have the heat on. Does anyone know what this could be? Car still drives ok, don't seem to be experiencing any power limiting.

Thanks!
I'm having this same issue. Thermostat was replaced and same U1408 and P0128. Do you have Bimmerlink? Try measuring your lower radiator hose coolant temp with that app and see if it's weird. Mine is. I wonder if this is the issue.
 

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I have had similar codes and issues, what ended up being the fix?
For me they first replaced the MAP thermostat PN 11-53-8-635-689. That did nothing and the car still wasn't coming up to operating temp in time. The oil temp would hang at 70C on the bottom end of the gauge - even after a 30-40 min drive. I also kept getting intermittent check engine lights for P0128 and U1408 codes.

I took it back to the dealer and they replaced the auto transmission oil cooler (heat exchanger) PN 17-21-7-600-553. There is second thermostat on this part that went bad. That solved the problem. My car now comes up to operating temp after a 10 min or so drive on the highway - even in very cold weather.

I can't find it now, but if you search the internet you will see evidence that this is a somewhat common problem.
 

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There***8217;s an extended warranty for thermostats stuck open 10 years 120,000 miles
 
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