What does 1997 Chevy Silverado Shift Actuator do ?

Question edited for clarity.
Question moved to model category.

Video here

https://www.google.com/search?q=1999+Chevy+Silverado.+How+to+adjust+the+shift+cable

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2 speed electric shift transfer case problems #1 jack up truck place on 4 jack stands. Start and select 4 high position in drive release brake ad watch front driveshaft does it turn "yes" problem is axle actuator on passenger side of differential not engaging axle shaft. "no" apply brakes bring to a stop engage low range does low range work "yes" internal transfer case problems "no" electric transfer case shifting motor failure.

First step is to check for error codes (DTCs) using a code reader and follow up if any.

check your brake lights, if there out it wont shift out of park, you will need a brake switch

First determine that the brake lights are working.
If they are, then the circuit that powers the shift lock actuator has power and it is a matter of determining if the actuator itself is bad or some other problem.

If you turn the key to where it unlocks the steering wheel, but none of the lights come on in the dash, you should be able to shift to neutral and start the vehicle. Make sure the brake is pressed and the park brake is engaged before attempting this.

Hope helps.

The shift interlock system prevents the shifting from PARK unless the brake pedal (2455) is depressed. The shift interlock system consists of a shift lock actuator (3Z719) mounted at the base of the steering column tube (3514). If the ignition switch (11572) is in the RUN position, the shift lock actuator is continually on unless the brake pedal is depressed. The shift lock actuator is the logical culprit. Check to see if it's getting voltage when the brake pedal is depressed. If yes: the unit is either faulty, weak or stuck. I can provide wire numbers and colors if necessary. I may need the engine size and Trans. code found on drivers door sticker. Good luck! Aoogha

check switch connections,fluid level and actuator at transfer case if good have truck scanned for possible trouble code possibleas sensor or component going bad , some auto stores such as auto zone /advanced auto do it for free if theres a trouble code it will be a starting point

start bleding again from left to rigt all the way around.

You can remove the interlock off the gear shift or maybe spray some crc on it otherwise probably a loose wire or switch

btsi solenoid on right side of steering column about halfway up column unplug and check green wire with test lamp while depressing brake pedal lamp should turn on and off if not replace brake lamp switch or check wiring if test lamp lights replace btsi solenoid