Truck Is Off, But Headlights & More Stays On!

Yesterday I found out that when I shut off my 2002 Tundra (4.7L V8) Ltd, 300k miles, the headlights stayed on. Opening the hood, there was also the faint whir of something running (keep in mind the truck was turned off and the key was removed). I removed the + wire from the battery and everything stopped. I connected the battery and everything stayed off... for a while. I went inside and came back in an hour, and the headlights were back on. I now leave the battery + terminal off when I stop the truck.

Today, I also found that the cigar lighter port was dead when the truck is running (I use it to charge my phone and run my dash cam.)

Maybe something is wrong with the ignition switch?

Any ideas?

 

I would check wires for rodent damage first, see if anything anywhere looks chewed. Check the cabin air filter, you will know if they got in there.

 

There's no cabin air filter on a 2000-2006?

 

Do you have any lights on in the instrument cluster or anything like that as in warning lights? Is it anything other than the headlights and what you think you may hear running?

 

Do you have aftermarket headlights that have fans in them?

 

Hey! Similar problem happening with my 06 DC, Was there any solution found?

Thanks!

 

Mine would act up occasionally after it's been raining but then would go away long enough for me not to bother checking why.

 

Sounds like something probably arc'ed out, OR someone has water intrustion into the fusebox, which is a really well-known issue covered in the megathread. Specifically:

• These trucks usually don't have a ton of other electrical issues. Hidden corrosion inside the battery/alt cables happens. Sometimes, a couple thousand miles after timing belt changes, people will have startup issues because the crank position sensor wasn't properly tucked away and gets rubbed by a belt (pic). There's also a similar problem with camshaft position sensor under the cam cover, where the belt will rub through (pics). There's the rodent issues mentioned earlier. Occasionally, water leaks can send water down into the ECM behind the glovebox (pics), or into the fusebox inside the cab/dash (pics and more pics). A lot of drain/vampire issues trace back to aftermarket add-ons whether the owner knows they exist or not - alarms as mentioned earlier, brake controllers, poorly installed trailer receptacles, those are some big ones.

But something as simple as arc'ing at the main fuse where the feed from the battery goes into the engine bay relay box could probably cause some weird issues too. If there's a relay between that engine bay fuse/relay box and the feed coming into the cab, I'd be eyeballing that also. And if you live in a rust belt state, corrosion inside harnesses is a VERY common cause of circuits staying open when you don't expect it - so identifying WHERE IN THE DAMN COUNTRY you are is pretty important.

Wiring diagrams are linked in paragraph 4 or 5 of the megathread, help yourself.