[leichtk]

I have a 07 N52B25, when I bought it I thought I'd check the codes and P0597 came up, I thought id need a new thermostat but there is no check engine light, anyone know if i need a new thermostat or from my brief research is it just the heater circuit inside the thermostat that isn't working and the thermostat is working fine??? no clue .. the car has the fuel economy gauge instead of oil temperature so I can't see if its getting up to temp, but seems to run completely fine.
Thanks

[gbalthrop]

Originally Posted by leichtk

... 07 N52B25... P0597 came up, I thought id need a new thermostat but there is no check engine light... I can't
see if its getting up to temp, but seems to run completely fine. Thanks

The "Bulb Heater" in the T-Stat opens the T-Stat at a lower Coolant Temp than it would open simply operating mechanically.
That P0597 code suggests your "Activation circuit" where the DME sends a signal to heat the bulb is NOT working. Here is the
BMW Fault Lookup "Fault Information" link:
https://bmwfault.codes/XMLDiagView?d...E4NjE5NDEwNQ==

The "Service Notes" at the bottom of that link suggest checking the wiring first. If you will provide the Last-7 Characters of
your VIN, I will confirm that the attached ISTA wiring diagram & Connector Location/View info is correct.

A proper Scan Tool, or INPA/ISTA Diagnostic Software can allow you to see Coolant Temp as reported to the DME by the
ECTS (Engine Coolant Temp Sensor), read the Activation Signal from the DME to the T-Stat, and also Activate the T-Stat
(if the wiring is OK). You can simply test the wiring using a cheap Multimeter. Check that fuse F78, 30A, is intact.
There should be Battery Voltage at the T-Stat Connector, Orange Wire, X6279/1, with Ignition ON, KL87 Active.
The White wire should have some voltage with Ignition ON, varying depending on Coolant Temp & Activation Status.
If you have a meter that can read "Duty Cycle" or Frequency, that will give better evaluation of PWM signal from DME.

If your car has an ROTS (Radiator Outlet Temp Sensor) on the Lower Radiator Hose (US cars do NOT), then that is
signal is also used by the DME to control T-Stat Operation. Confirm visually if that sensor is present.
If questions on HOW to do any of that, please post back.
George

[leichtk]

thank you for your reply, greatly appreciated
unfortunately i have not a clue how to do any of that, so theoretically if i took it to a mechanic how much would that cost?
Thanks