I have a 2007 Toyota Tundra and the 4wd does not work, when I turn the button lights 2h to 4h to 4l light and makes a beep and the light pulses

sorry, q sensor could be? And if that is the only way to see which sensor is only with the computer? will explain step by step, every time I turn the engine lights 4H and 4L are pounding and when I turn the button of 2H to 4H begins to sound an alarm 4L and the light begins to throb, my mechanic is an revised and not an found nothing wrong and my other question is whether there is any procedure to enable or repair the 4WD because my vehicle is repaired by an accident, you agradesco much for your time. sorry, q sensor could be? And if that is the only way to see which sensor is only with the computer? will explain step by step, every time I turn the engine lights 4H and 4L are pounding and when I turn the button of 2H to 4H begins to sound an alarm 4L and the light begins to throb, my mechanic is an revised and not an found nothing wrong and my other question is whether there is any procedure to enable or repair the 4WD because my vehicle is repaired by an accident, you agradesco much for your time.

" thank you very much sir, this OBDII only Toyota has agency? my computer is a SNAP-ON MODIS 8.2, but I diagnotica no bad sensor on my 4WD, it only appears airbags, air sensor in the tires, if neither diagnosed tranfer (4WD), you had no this happened before? and if so q was or what happened to this, is to get an idea of the problem and I'm from HONDURAS and not easy access to a good computer or the agency since that does not get vehicles from other countries like the tundra 2007, again thank you very much for your understanding and time. " " thank you very much sir, this OBDII only Toyota has agency? my computer is a SNAP-ON MODIS 8.2, but I diagnotica no bad sensor on my 4WD, it only appears airbags, air sensor in the tires, if neither diagnosed tranfer (4WD), you had no this happened before? and if so q was or what happened to this, is to get an idea of the problem and I'm from HONDURAS and not easy access to a good computer or the agency since that does not get vehicles from other countries like the tundra 2007, again thank you very much for your understanding and time. "