I'm working on a friends 2008 550i that has the following code: P0598 ( Thermostat Heater Control Circuit Low ).

I changed out the thermostat housing with a Koolman housing and cleared the code and it keeps coming back.

I checked the resistance on the oem sensor and it came out to 15.7 and the new Koolman came out to 16.7. Does anyone know if these values are okay? I'm afraid it may be the wiring but have no access to schematics nor know what values that plug should have ( voltage? ).

Any thoughts?

 

I don't know that Koolman is a bad part, but I wouldn't have used any brand that you don't see on the popular sites like ecstuning.com, autohausaz.com, etc.

 

I didn't buy it. Can anyone unplug theirs and check the voltage on the plug and resistance on the element?

 

Thank you for the mention, twh.