New user here, forgive me if I did not post this correctly.

Issue: 2001 C5 driver's turn signal light stayed on all the time even with car off. Driver's turn signal did not flash when left turn signal activated.

Thanks to the many folks who have described this issue in this forum I decided to swap DRL relays 38 and 40 under passenger foot panel. One relay (38) was pretty hard to pull out, had to pry under its base with tiny screw driver.

Fixed! Everything works as it should. Since the problem did not switch sides I can only assume that the relays were fine, one or both just had developed poor electrical connections. I got lucky. I was about ready to order an rebuilt BCM online per dealers's recommendation and have them flash it.

Thanks to all the folks on this forum for providing all the good information about this known issue. This solution is much better than driving around with fuse 2 pulled (engine compartment) which is what I was doing.

All exterior lights except headlights have been switched to LED. Special LED harness installed which produces a normal turn signal flash rate. Hazard flash rate is about 5 times higher than normal but with the quick responding LEDs, I am ok with this.

32,800 miles on the car.