I recently bought a 2007 Aura. 125k. It had been garaged for about 8 months. 1st week everything was great. But, Every night since Monday, at some point during the night, the headlights come on by themselves. Monday I noticed them on about 11 PM. I thought I had done something wrong I went out, cranked the car and turned the lights off. Didn't thing anything about it. I was off work Tuesday and slept in. I went to leave around lunch and the battery was dead as a hammer. I went to jump it off with my other car and as soon as I connected the cables, the lights came on. I started the car and let it run a while to charge the battery. I drove the car all day with no issues. Wednesday morning I got up around 5:30. I looked out and the lights were not on. I got ready for work and came down stairs about 6:30, looked outside and the lights were on. I went out, the battery wasn't dead. I turned the lights off and then went to work about 30 minutes later. No issues all day. This morning, the same thing happened. I looked out about 6:00 and everything was fine About 30 to 45 min. later I came downstairs and the lights were on. I turned them off. Went to work later and no issues all day. I've talked to a couple mechanics and nobody has any idea. I don't know what to do. Does this make any sense to anybody??? Help please!

 

Is this just the headlamps or are the running lights also misbehaving?

Try setting the switch for the lights to manual "off" instead of leaving the switch set to "auto". Actually I don't know what you currently do, but please try the above.

I do not have Aura wiring diagrams.

CONJECTURE:

The first thing that comes to mind is the daylight sensor, the output of which controls when the car switches from DRL high beams to what should be low beams + running lights if the switch is set to auto.

The light sensor output circuit would close/become continuous, triggering a request to the BCM to close the low beam relay and the running light relay. However, this can only be expected behavior with the lights set to "auto" and the ignition switch on or acc, so that the auto functionality does not occur with the key in the off position or your lights would cycle at dawn, dusk, and stay on in the garage.

It's also possible that the light switch itself is defective and sending spurious requests to the BCM to turn things on. If only the high beam headlights are coming on, it's thinking it is in DRL mode. If only the low beams are coming on w switch in auto, then I would suspect the switch since the low beams should never be on without the running lights.

Could also be a relay issue, but for it to physically close w no ground provided seems highly unlikely. Furthermore, you are able to turn off the lights and they do not come right back on.

Like I said, all is conjecture for now.

See if you can track down some wiring diagrams.

 

Any updates?