Having issue shifting in/out of 4wd. I cleaned the actuator. After a test drive it was still bad so tried 4lo and now its stuck in 4lo and both indicator lights are flashing

K or savana 1500? I will guess K1500 4WD.
driving on snow or offload?
4Lo, shifting is best at 1 to mph, a dead slow crawl.
what transfer as is here.? (RPO list not told or VIN)

NV241c
NP243
NV242

SOME ARE FULL TIME OTHER PART TIME,
SOME HAVE A LOCK FOR PART TIME MODE.


for sure this truck is not AWD all wheel drive (not full time)
if not off road/or ice. it puts huge strains on the drive line.
in 4wd the axles clock.
The 4L and 4H are for offroad only, and on ice.
not pavement free of ice.
you will lock and wind up the axles and will not shift out of 4wd
and steering fights you (see that)
to cure this windup, move one or more tires to ice or dirt. and shift
slowly at 1mph or less.

page 2-22 in your glove box manual states and I quote





RTM, see this means not full time AWD

when tires are on ICE you are in effect, offroad.

Which transfer case does it have ????

Is the service light on ?
SERVICE indicator (4WD/AWD) Lamp
The SERVICE indicator (4WD/AWD) lamp is an integral part of the cluster and cannot be serviced separately. This lamp is used to inform the driver of the vehicle of malfunctions within the automatic transfer case (ATC) system. The SERVICE indicator (4WD/AWD) lamp is controlled by the transfer case shift control module via CKT 1567.
Circuit Description
The ignition switch supplies Ignition 3 voltage to the transfer case shift control module at connector C1 terminal E10 using the 4WD Fuse. When the ignition switch is first turned to the RUN position, the transfer case shift control module responds by flashing the SERVICE indicator (AWD/4WD) lamp for approximately 2 seconds, then turning it OFF, while performing tests on the ATC system. The transfer case shift control module will continue to perform tests on the ATC system during a normal drive cycle.

Hooking up a factory or some other professional scan tool that can view DTC'S - diagnostic trouble code's in the 4X4 control module would be the best way to find the problem.

DTC B0768 Service Indicator Circuit High
DTC B2725 ATC Mode Switch Circuit Malfunction
DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
DTC C0308 Motor A/B Circuit Low
DTC C0309 Motor A/B Circuit High
DTC C0310 Motor A/B Circuit Open
DTC C0315 Motor Ground Circuit Open
DTC C0323 T-Case Lock Circuit Low
DTC C0324 T-Case Lock Circuit High
DTC C0327 Encoder Circuit Malfunction
DTC C0357 Park Switch Circuit High
DTC C0362 4LO Discrete Output Circuit High
DTC C0367 Front Axle Control Circuit High
DTC C0374 General System Malfunction
DTC C0376 Front/Rear Shaft Speed Mismatch
DTC C0387 Unable to Perform Shift

check for vacum leakes. check the 4wd actuator located under th battery box. I uses vacum to pull in and out of 4wd

the actuator is known to stick and or seize on the 4x4 jack up and secure vehicle the actuator is on side of transfer case check wiring and connections at actuator if good than u can use a rubber mallet tap around actuator to loosen any road debris which sometimes works but the best is to test and if good to unbolt clean and lube actuator and shaft and replace

Try shifting the transmission into neutral then pressing 4hi. It should flash and then engage. Shift into drive again and re-try. Anytime shifted from 4hi to 4lo it needs to be shifted into neutral during transition. There is no need for 4lo position, unless you are really stuck off road, in the mud up to the windshield. Do not use 4lo unless you 4WD off road.

Disconnect the battery for 30 minutes and try again. Be sure to follow the correct procedure for shifting from 4lo to 4hi or 2wd. That would be: engine running, transmission in neutral, foot on brake, shift to 4hi or 2wd. If it is a push button shift, hold the shift button in for a few seconds. If you hear the shift motor actuate, put the transmission in reverse and back up a few feet. If that does not work you may have a bad shift motor.

what you are most likely feeling is in 4lo the transfer case drops the gear ratio and 4hi just locks the front differential in. do you know if the front axle is locking in in 4lo? i suspect you have a vacuum issue to the front actuator and this is why. there is a vacuum switch on top of transfer case that will stick and cause problems and sometimes the vacuum lines will pop off of this switch.check and see if you are getting vacuum to the actuator if not follow lines be sure one is not broken if you are then actuator is bad

@ 2000 gmc: Exactly right.

asker: Also, it helps if you're rolling at about 2 mph with the steering wheels straight.
You cannot shift into 4LO with the wheels turned or when in a drive
gear. Also, it may be that you need the electric shift unit serviced.
It is not recommended to drive on dry pavement while in 4LO.

Change shift solenoid

it is either the control switch or the actuator. look if light is flashing on push button switch. if so it is stuck. you can check actuator on front axle, to watch and see if it is moving.