Bought an ‘05 Titan and never figured out why the battery dies if left unstarted 2-3 days. Only today I discovered the Drivers AND passenger Window switch lights stay illuminated all the time, even when truck is locked and left alone. Seems like the power to the switches is no longer switched with the ignition, but huh?….. I found the 50a/30a/30a BCM/PwrWdw multi fuse that does cut power when pulled, but switch lights just come back on when fuse plugged back in. This is why battery dies, but where’s it getting constant power from?!
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The way to learn the answer for sure is to find or buy a wiring diagram for the vehicle, which, combined with your multimeter, will tell you where the problem must be. You could buy a short term subscription to an online automotive repair data service.
Meanwhile, probe the fuse block(s) for other circuits that should be off, and if you find more, suspect a defect in the ignition switch. You might also insert the key and wiggle / force / abuse the ignition switch without actually turning to "ON" to see if the window switch light turns off.
You might also try disconnecting the battery for 30 minutes, then reconnecting to see if the window switch lights come back on. If not, a module (body? convenience?) may have been suffering from temporary insanity and remaining on all the time. In that case, it could happen again.
And finally, you might be barking up the wrong tree and the lights are supposed to stay on. Two little LEDs drawing perhaps 50 mA combined would take weeks to drain a car battery. You may have a much bigger current drain somewhere else. You'll find many questions / answers in this Stack on finding a current drain.
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