P0599 2005 x5 please help...
 

Hi pro's
I am getting P0599 on my 2005 x5. It this always thermostat ?
I don't have any drivability or over heating issues.

What to look for as proper diagnosis ?
Any ideas

Diagnostic steps on this page: https://www.obd-codes.com/p0599

First things: coolant level full? Check wiring to the thermostat the error is saying there's a short in the tstat circuit.

Secondly: check the actual temperature of the coolant with the hidden menu. Reset the code and from a cold start see what the temperature is when the code trips.

I would say very good chance the internal electrics have failed and you will have to replace the thermostat. Not a terrible job, one of the first did on my X5. Don't try to avoid removing the fan is not worth the effort.

Thanks for the approach.
I did coolant flush as it was due anyways yesterday and code still came after reset.

I did thermostat replacement 6 yrs ago and yeah i did remove the fan and easy job. Just wanted to confirm if thermostat was the real issue before replacement. Will check the connectors and temperature as suggested

After replacing the thermostat it couldn’t hurt to replace the temperature sensor as well... what engine do you have?

Also a cracked coolant resivoir is common on this series of vehicle.

Since the error is specific to electrical fault (short high) first try to rule out wiring including disconnect connector If the internal sensor/heater shorted out giving the error the problem will migrate.

Example: you are getting a shorted high signal that should happen if the wiring has an insulation break and is shorted across two wires (hot and signal). If you unplug and still have the same error the short is in the wiring.

If you unplug the tstat and the error becomes "open signal to tstat" well the. You have your answer: short internal.

You can probably find online what Ω values the connector to the tstat should read. I don't even know how many wires it has or if it's a temp sensor or heater or both. I thought it was both .

I have 3.0 and yes you were spot on the darn expansion tank blew on the highway 5 yrs ago and i replaced that along with the hoses.
There is no loss of coolant from that point. If i do the thermostat i will replace the temperature sensor as well.

perfect aproach to rule out if tstat is the issue or wiring. Will also check the resistance. Will try that and update the thread.
Also this code p0599 seem generic from a obdII scanner. Do you think there would be specific hidden BMW error code totally different ? just a thought

Doubt it the "generic" code is pretty specific "tstat high voltage" or such


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