P0599 + Thermostat - What Does It Really Identify / Do?

[Bluemach1]

2006 X5 3.0i


Hey all,
So I have a P0599 code. I know how to troubleshoot and replace.


What I do not know is, what is the P0599 actually an indication of failure of (beside the circuit failure)? Is it simply only indicating the sensor failure? I have no overheating or loss of fluid.


I guess another way to ask this question is, in fully working order, what is this sensor really for? Since my temp gauge reads fine, is this just a redundant warning mechanism?


I also assume that since I do not show any other temp issues or leak issues, I am safe to drive until I can get around to replacing. True?





Appreciate any knowledge you can impart.

[Clavurion]

It's not a sensor. It's a heating coil to "fool" the thermostat opening earlier on high load.

https://www.pss-autosoft.net/diagram...1214_M0KFK.htm

[Bluemach1]

Thanks for the explanation and the link. As I live in a very mild climate I wonder how often that actually comes in to play for me? Anyway, now I have a full understanding.

[X5chemist]

Nice link. The article will be added to my X5 reference notebook.

[Fifty150hs]

Originally Posted by Bluemach1

Thanks for the explanation and the link. As I live in a very mild climate I wonder how often that actually comes in to play for me? Anyway, now I have a full understanding.

Typically kicks in when the engine is up to temp and you're driving on the highway. It lowers the temp by opening the stat thus increasing horsepower a little. If you unlock the cluster or plug in a scanner you can watch as it does it's thing. You can get on the highway with the engine at 203 and it will pretty quickly drop to as low as 187, at least on my 3.0.