wow, this is a busy board. :bump:
I've got similar problems. They happen then go away for a year or so.
Most likely is GM5. Send it off and let 'ole dude fix it for you . I took apart the doors and tried putting white lithium grease on everything. Didn't help at all. Just made a huge mess.
Also, when mine does this, and I finally get back into the car, here is how I fix it. I keep hitting the central locking button until it starts working. Then keep pushing the button. It's kinda like it works out the kinks. It doesn't happen for a LONG time after that. Not a good long-term solution, but ok for a while.
From my experience if the door locks fails to unlock and the problem comes and goes then it's the general module. It's not the actuator, it's not something that needs to be lubed.
If the problem is failure to unlock and it's a solid failure (not intermittent) then it's most likely a bad actuator. This is more common on coupes and convertibles for some reason.
Your problem is intermittent, multiple doors of your 03 4-dr sedan do not unlock, worse in hot weather. That problem IS the general module!Thanks for the input scottjoh. Is there anyway to troubleshoot/verify before repairing/replacing the GM? I can get to the GM & I have tools including a multimeter.
Thanks Scott! Awesome turn-around on the module and quick responses. Sent it priority on Tuesday and had it back before Friday. The instructions made it easy to remove/install, and I didn't break anything. Bring on the summer heat! :evil:Thanks for helping to clear that up. I'm away from the house for a couple months. Guess I'll take care of it when I get back.