A 2001 BMW 325i has two coolant temperature sensors. They constantly monitor the temperature and adjust flow as needed.
The temperature sensor on a BMW 325i is located on top of the engine, near the upper radiator hose. It constantly monitors the temperature of the coolant and triggers the cooling fan as needed.
P2185 is ECT sensor high voltage detected. ECT stands for Engine coolant Temperature Sensor.
you may need to replace the sensor for the coolant, there should be a wire connected to it.
in the intake air box
that's a big negative
is in hard to replace a thermostat on a 2001 bmw 325i
BMW coolant from dealer. It is blue in color and can be purchase fairly cheap at any BMW dealer ship. Around $20 for a gallon. Hope this helps.
think you will find it under the drivers side bumper, it looks like a round disk.
If you have a 1989-1995 model 325i, the ambient temperature sensor should be part # 65818350779. Best way to see a picture is do a Google image search on the part number. It will look like a plastic piece, black on the probe portion, yellow on the plug-in portion, with 2 round electrical connector pins.
Water
How often need to change the fuel filter for a 2001 BMW 325i?"
It is just behind and below the air filter housing. The air fiter housing and air temperature sensor coolant lines do tend to get in the way. When I checked mine recently, I found it was easier to just remove the air filter housing.