4X4 indicator light

2005 tacoma 4x4 with the differential lock button. Niether work and the 4x4 indicator light on dash is blinking. Is there a typical problem that I should look at first or is it anyones guess

 

I’d start here.
This 4WD system can be frustrating to diagnose

https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

The diff lock will only function in 4 Low, the flashing 4wd light indicates the 4wd ECU was unable to complete a shift or a limit switch is out of the expected range.
Withe the age of the truck it would be a good idea to check the vent hoses on the actuators, if either is disconnected water and dirt can get inside and mess up the contacts, sometimes they can be taken apart and cleaned other times they must be replaced.
Alot of info about the system compiled in the thread @TnShooter posted above.

 

@TnShooter is right, start there.

You need it to engage 4L before you can turn the locker on.

 

If you need some encouragement; I was able to fix my 4wd system with the info here on the forum and now it works great.

 

First things first. KISS METHOD.

Like stated you need to be all the way in 4lo for the rear locker to work (stock thats how the system is).

To get into 4lo you must be FULLY into 4hi first, be under 3mph in neutral (auto) or clutch fulllly depressed (manual) then shift to 4lo.

To get into 4hi you can shift from 2hi to 4hi under 60mph on the fly (recommend to be rolling around 10mph or so in a slight arc).

If you cant get into 4hi, you wont be able to get into anything else.