This is a new issue for my 2006 Prius. All seemed to be functioning normally until recently. Now, when my headlights are on, and the highbeams are off (highbeam lever pulled back), when I shut my car off, my highbeams come on. I then have to push the highbeam lever forward to shut them off. When the car is turned back on, if the headlights are turned on, the highbeams come on. I have to pull the lever back to shut them off. In other words, the correct "on/off" position for the highbeam lever is dependent upon whether the car is turned on or off. This has resulted in a number of occasions of my parked car being left with the highbeams on, draining the battery, and me coming back to a dead car. I have "rebooted" my car by unplugging the negative battery terminal for a half hour, but this didn't solve the issue. Any thoughts?
To start with cheap stuff first, check the headlight relays. They're called DIM and H-LP, in the main relay block in the engine room. You'll need a wiring diagram, a 12V source, and an ohmmeter. If the relays and associated wiring are okay, the body ECU may be malfunctioning and that's not cheap. Wiring is different for HID and DRL options. Good luck.
