The fuel sending unit malfunctioned around the same time as the electrical system failures. The fuel gauge would drift to either end slowly and finally settle at empty most of the time. Had sending unit replaced for about $400 but it had no effect on the power loss issue that would drain the battery if the headlight delay was turned on. I don't carry a spare battery anymore but I do carry a charger, cables and a long extension cord.

I have a suspicion that the two issues are related as the fuel gauge is connected to the computer for calculating usage and fuel range. GM offered to re-program the computer for about $125 which may be the key to it all. Or replace the headlight timer for $100. This should have been a GM recall item as it is not an isolated occurrence on these cars.

So did the faulty fuel sending unit cause electrical damage to the computer resulting in the headlight timer and dead batteries???

It's a shame that GM will not do anything about this problem when it has been reported happening on many cars and is even noted in one of their service bulletins. The 2001 LeSabre is the last of the full size Buicks having run for about 4 years (2000-2005) with the identical body style. At least there will be many LeSabres in the wrecking yards for years to come for interchangeable parts. This is a really great car to drive and has their most reliable 3.8 engine which is still used today in the newer models.

The only real pain it has given me is when the front marker/running lamp bulb went out and in order to change it the entire plastic apron under the front of the engine has to be removed to change the lamp. Lots of plastic panel retainers have to be pulled apart and reassembled for re-installation and the front of the car must be up on blocks to access them. Replacing both lamps is a must so I won't have to go through that again for a while.