OK, I have PLENTY of washer fluid, yet the annoying message is on my instrument cluster all the time now. It used to pop on and off once in a while and I didn't think much of it, but now it's really pissing me off. Any solutions/troubleshooting advice? Thanks a lot.
P.S. I recently installed those HIDs from the other thread from eBay, and am generally pretty happy with them; sure can see a lot better at night.

well maybe during your install u accidentally unclipped the sensor from the washer tank?

those sensors are a known failure item on E34's, you can either a. replace it, or b. jump the sensor so u dont get anymore messages.

Ahh the sensors in the e34...gotta love em.:mad If I recall some other posts correctly, it should be cleaned, and some sort of "protectant" against corrosion applied, but others will know more.

I would like to hear more about how to fix this as well since my car does it all the time.

The sensor wires should point straight up; sensors rotate easily by hand so it's easy to accidently turn them when working on headlight wiring. Touring message wasn't updated so either front, rear or both give same message. It only takes about 5 minutes to remove, check & replace a sensor for continuity.

Mine did this as well, but in my case the tank is cracked so until I get a new tank I pulled the conntector off of the sensor and put a jumper across the pins and no more message.

OK, the tank is in the front left corner of the engine bay, and it says 3.1 liters on it. Is that it? There is a hose and a wire probably all tied together with insulation tape that are running to the tank, but I don't really see any sensors in the immediate proximity. Any more detailed advice? I'd like to resolve this. Thanks again.

Could Be Mis Aligned Sensor, Bad Sensor, Or Wiring Problems.

On my 540 if you look down inside the tank you can see a float this is the level sensor on mine it's on the back side so where ever it is on your tank look there for the connection it's just a switch so when it's up it's closed and down it's open

You can just run a quick diagnostic check on it and just clear the fault that was aswell if nothing seems to be wrong with it otherwise.