202- ES350
So last week we got home and turned off the car like we always do. Next day we went out to go somewhere and my wife says the headlights were on. I look at the drivers side and it was off. Looked at passenger side and it was on! Of course car wouldn’t start but battery didn’t get low enough to reset everything. Jump started it and drove it and the battery charged back up. Never happened before or since. Anyone see this before? Why would one headlight remain on?

 

How old is battery?

 

If it was me I'd make sure both headlights go out every time I shut the car, at least for a dozen or so trips.
Sounds like a sticky relay contact.
I never liked or trusted that auto-off delay feature.

 

If I'm not mistaken, the headlight assemblies are controlled by commands sent over the CAN bus to the left and right headlight ECUs. There is a separate branch of the CAN bus to each of the ECUs. If there was some sort of temporary glitch on the CAN bus branch to the right side/passenger side headlight ECU preventing a decodable turn-off command from reaching that side's ECU, that could cause that headlight to remain on when the other side's headlight turned off.

If you have access to an OBD II scanner, you might try checking to see if any DTCs have been stored indicating trouble with communications on that CAN bus or some other type of headlight issue.

 

I had no idea the headlights were ECU controlled and were involved with the OBD system. Way too much complexity for such a simple function imo.

 

Got it last July. Interstate. It powered that one headlight all night and half the next day!

 

Thanx I’ll check it out.

 

even more reasons for you to re-purchase 1999 avalon

 

Agreed. It was the perfect combination of bulletproof reliability, simplicity, power, and comfort.
It had a bench seat and column shift!
New England Winter salt did it in. The drivetrain, accessories, and electronics were still perfect.
RIP '99 Avalon

 

Never buy a BMW!

 

 

had 7 bmws, never had issues w/ computer controlled headlights. i did however have everything leaking oil all the time, even after repairing them. lol.