just encounterd this two days ago. came back from lunch and headlights won't shut off as well as parking lights and instrument panel lights. I turn the auto switch to off and no response. Won't even say "auto lights off" on the dash. only way to get the lights off is to pull the low beam relay, park light relay and IPC cluster fuse at the BCM.

First thing was check all fuses and all good and check for codes and none found. Went into the BCM module and looked for codes there as well and none found. Swapped relays 71 and 72 and even tried a new relay but didn't fix it. Second fix was put a new headlight switch on. Put the relays back in and didn't even touch the switch and headlights right back on and still no "auto lights off" message when turning the switch. Disconnect the wire harness to the new switch and all the lights shut off, relays still in. Third fix attempt was a new ambient light sensor. No change.

Today, I disconnected battery for 30 mins. While the battery was unhooked, I put all relays back in. After 30 mins I hooked the battery back up and to my surprise no lights on. Turned the headlight switch to Auto off just to see if it would respond and it did and I got the message on the dash "auto lights off" and the accompanying chime. Turned the switch to park lights and park lights responded on. Turned switch to headlights and they responded on. Flicked high beams and they responded. Turned the headlight switch to off and now won't respond, lights stuck on again. Almost like once the lights are activated it locks the relays on. Unhooking the battery seems to "reset" everything until you turn the lights on again.

Looking back on past posts from this site, it seems to point to either short to ground or BCM. I am no wizard with wiring schematics but having looked at the lighting circuit diagram in Donbrews link to shop manual, it appears that the only way the lights would light up is if the relay is energized from pin #86 on the high and low beam relays. Lo beam is triggered from the on/off switch and high beam by ground in the BCM. In reality i guess they're all controlled by ground from the BCM. the only other way would be if there were a short to ground on the pin #86 wires after the BCM which I find hard to believe I'd have a short for parking lamps, headlights and IPC which would be three seperate wires.

What testing can I do to start trying to pinpoint the source? I didn't do any recent work on the car. Not having any other problems with the car. Theres is nothing else acting up that would make me think BCM but apparently these cars are know for BCM issues. I hope that's not true.

As always, I appreciate the input from everyone on here and also a big thankyou to Donbrew for that link to the shop manual. It has been priceless.