Failure Code 597, temp only 75 C

[Acond]

Thanks for good link with instructions how to test. Forgot to inform that in the meantime I measured the resistance of the heater unit in top of stat cover and found it is about 18 Ohms when Service Light is not illuminating (engine cold). When I drive the engine warm and Service Light start to illuminate resistance climbed higher than 4 Mega Ohms - practically open circuit. This made me think that need to change the thermostat assembly. Already ordered the part. Hope this was right decision. I repeated the test several times. When engine cold no light and low resistance, after ten minutes when engine getting warm light illuminates and high resistance. When engine hot and I put the ignition on the service light starts to illuminate within e.g. 10 seconds, when engine cold I did not wait more than 1 minute but the light did not come on. This 18 ohms correlates pretty well with this link below. Really hope I made a right diagnosis. Can be of course control module K20 problem with this code or any wire/connector failure but let's see. I report my findings after having changed the thermostat ass.


https://www.youtube.com/watch?reload=9&v=mk020n9-SPk