I have this same problem and luckily came across a mechanic that had fixed it before. In my case my ex had been driving with a low tire for a few days. It was explained to me that a low tire technically has a smaller circumference, since the bottom is compressed inward, to the cars sensors it doesn't say "oops, low tire." it says "woah that tire needs more rpm to keep up with the rest (large cylinder vs. small cylinder in comparison to the tire sizes and needed rpm to go a certain speed) It must be slipping! so it turns on your automatic 4 wheel drive. Now, you're on dry ground as this is happening which is BAD, this ruins the motor that kicks in the 4 wheel drive, the clutch mechanism within gets ruined when the plates warp and been, which makes the automatic 4 wheel drive turn on at all times. What you need to do is bring it to a mechanic and have them drain the fluid from the automatic 4 wheel drive motor, if it's black, the clutch is ruined. This can be fixed by taking the motor off and saying "goodbye" to your automatic 4 wheel drive, or by replacing the motor and clutch system. If you let it go on long enough it could ruin the transfer casing which is extra expensive on the 04 ranier because it's made from a solid block of aluminum as opposed to cast metal like a majority of other cars.
Sorry for the long post, hope it helps!!
...had to make a stupid account to post this
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