2013 F10 M5 Thermostat Stuck Open

[x35250]

I have a 2013 BMW M5 weekender. Stage 2 custom tune for the past two years.

A couple months ago, I had a CEL about 45 minutes into a drive. I was pushing it a bit (nothing crazy) on the highway - M2, Sport Plus throttle.

The error codes were as follows on my BM3 tool:

Engine (DME)
1D2008 - Mapped thermostat stuck open
1FB201 - Check Control message (ID 257): Motor too hot! Drive moderately
10AA30 - Coolant temperature sensor: Group error

Engine (DME2)
109210 - Mapped thermostat, coupling stuck open

The engine is not overheating because the coolant shows to be about 185 degrees F while the engine oil temp is about 190 degrees F.

The car is actually overcooling. It struggles to keep the temp at operating temperature. Stopped at a long red light, the temp gauge will drop from operating to a little above the 160 degree mark.

I took the car to my Indy shop. The tech said the thermostat was crazy "lazy." The thermostat was replaced. This seemed to work for a couple weeks. The engine got to operating temperature much quicker and stayed at that temperature for the entire drive.

Today, however, while driving on the highway again on M2 with Sport Plus throttle response, the same CEL codes popped again.

I did flash the xHP Stage 2 map right before this problem first began. I flashed back to the stock transmission tune to rule out some sort of conflict with the DMEs and the xHP map.

I also changed some of the custom tune parameters on the BM3. Changed Max Cooling mode to Original from OEM. Changed TMAP Sensor and TMAP Sensor (Intake Manifold) to Original from OEM too.

I already searched the forums but there doesn't seem to be a lot of literature on the thermostat stuck open code for the F10 M5s specifically.

I already spent a lot of money to replace the TMAP sensor. Hoping this won't cost me a lot more money to hunt down.

[x35250]

Flashed the xHP back to stock and I am still getting the error codes.

Fan is running extremely hard and loud when this happens even though the engine oil and coolant temps are below operating temperatures.

Coolant is about 165 to 185 and oil temp is in the 180s as well. The car is not overheating at all even though the error message says the engine is too hot.

So annoying. This has been very reliable other than this issue.

I don't think it is a water pump issue since the cooling system is working fine.

Maybe the coolant temperature sensor is the next thing to try? Easy DIY.

[M5Rick]

So many sensors on these, yeah change out that temp sensor if it's an easy job.

[x35250]

Update:

It was a tuning issue. The Indy shop that tuned my car adjusted the Max Cooling parameters for the map. I'm not sure what caused the issue in the first place since I was on the same tune for over two years. Either way, the car now gets up to operating temperature a lot faster and holds it well.

[Solo_M_Tech]

Shocker. I’d request they pay you back for the thermostat that wasn’t defective too.