Headlights, turn signals, door locks (via keyless) just stopped working.

Took our 2003 Honda Odyssey to the garage after all of the lights came on in the dashboard, assuming it was the alternator as it went a few years ago and did the same thing. The garage said yes, alternator, and replaced it only charging labor because it was still under warranty. Went to pick it up 3 days after it was done (I was having surgery and couldn't get there the day they finished) and the battery was dead. They recharged it, got it running, but the locks on the doors wouldn't work. I noticed because I tried to unlock it to put something in the back and I couldn't get the doors to unlock. I can use the actual key in the door manually and get the front driver and passenger doors to unlock that way, but the two back doors are the automatic ones and they won't open. If you are in the car and hit the lock button on the door to unlock or lock you can hear a slight, electronic clicking sound as if it is trying to work, but nothing happens. If I reach in and manually unlock the back door it just slides right back locked again. That has never happened before. We've always been able to manually unlock the back door from the inside. The hatchback won't unlock either (and unfortunately that manual key entry is rusted and won't let me turn it). If I use the remote and press the lock button nothing happens. If I press the unlock button, the lights come inside and the flash on the outside the way they always do when the locks were working, but nothing else happens. The garage kept it for two more days and they say they have run all of the diagnostics on it and just can't figure it out. They did say that whatever is wrong with it also seems to be draining the battery as the battery consistently loses a charge while the car is just sitting, not being driven. I've made an appointment with the dealership to look at it next week, but I'm wondering if anyone has any thoughts before then. The dealership will charge me $100 just to look at it. I hate to not fix it because it's still a great car with not a lot of mileage for the age, and we can't afford a new one, but I also don't want to dump a lot of money into an eleven year old car.

My 2007 touring odyssey has been doing similar problems:
I call it electrical lupus as one item after another stops working.
The first thing to mess up was a parasitic battery drain; 24-48 hrs to drain the battery.
Next thing to go was the driving lights, then the rear camera.
Both high beams stopped working at the same time. Then, not all at the same time, but the rear hatch closer stopped working, wipers only work on fast speed, power door locks briefly screwed up.
Wipers currently may or may not work on something other than high speed.
For the lights, I have done the obvious - replace both high beams, replace both DRL's, replace DRL relay, replace combo headlight switch on steering, replace each headlight fuse, replace DRL fuse.
I disconnect the negative terminal every night due to the battery drain.
I am out of ideas.
Will look into the panel areas to see if there is a moisture problem, but hope there would be more specific info at what I am looking at - maybe pics.

I've been getting email updates on this post from 2012. The issue was never resolved and we have moved on from our 2007 Odyssey EX-L.

The car continued to exhibit electrical and mechanical issues up until last year. Ending with the A/C disintegrating, steering rack and tie-rods failing, and finally the alternator went bad on its last use. Put a new battery in and drove it to the dealership. Got $1,000.00 on trade in. Bought a new 2021 VW Atlas SE R-Line. Great vehicle. AWD, three rows, plenty of towing capacity. It was also less expensive than the Current Odyssey.

Again, thanks for all your posts and suggestions.

I know this is an old post, but wanted to add something additional and see if it could be part of the cause. I am just now having this issue on my 2005 Honda Odyssey. I really like this vehicle as it has lasted a long time with few problems until now. I am exhibiting the same symptoms; key fob not working, door locks wont work, low speed wipers, outside temp gauge, and turn signals. A while back the automatic doors stopped working and we have just been manually opening them. We looked at the TSB for this issue and also some other fixes regarding water leaks that might be the cause. However, what I found mainly due to finding the battery dead one morning, is that if I disconnected the battery and after cleaning the posts reconnected it suddenly everything started working, including the sliding doors. But then the next morning I found the battery dead and right back where I started.

My question is, could a bad battery be the cause of all these issues? I am planning on having the battery tested today, but wanted anyones thoughts on if I should be looking for something more electrical or it's just a bad battery? Hopefully the battery is the cause as that is a relatively low cost repair.

Thanks for the response. They tested it and said it had a weak charge. I ended up going ahead and replacing it as it was quite a few years old. However, by the time I got home, I found that the problem still persists. I think I am at the point where it is beyond my know how and plan to take it to my mechanic to have a look. Being that it's a 2005, I might opt to upgrade to a newer model and not dump much more money into it. I really don't feel comfortable taking it too far and/or driving it around with no turn signals.

If I do pursue getting it fixed, I will start a new post with any new information.