Readjust the cables down by the actuator (watch installation video again). Loosen the cable adjuster so it has a little play when in 4WD. Rotate the knob to the 4WD position and pull it out because sometimes a little piece of metal can stop the cable clasp from locking into the hole.

Check to make sure the 2-pin connector is plugged in. If it is not, the 4WD light will come on and stay on. 
A microswitch may be stuck inside the tank lever as well.

Check our microswitch and activate it by hand to see if the display changes. If it does, bend the switch out a bit so it makes better contact with the cable clasp. 
If it doesn’t change when hitting the switch by hand, unplug our 2-pin connector. The OEM setup should display 4WD. If it still says 2WD, there must be a short somewhere between the OEM wires and the 4WD control box.

Did you remove the KEBC actuator?
Is the belt switch bypass plugged in?
Double-check all connections! Must perform a belt light reset procedure with our kit installed.
It could be a bad 4WD control box, a broken wire between the 4WD switch and 4WD control box, or between the 4WD control box and the main ECU.

Unplug the 4WD actuator, try riding around, and see if it still happens.
If it still happens, plug the 4WD actuator back in and remove the 4WD control box (speedometer will temporarily stop working), then ride around and see if it happens again. If it does, it is your 4WD control box.

The customer may need our actuator spacer. The shaft on the actuator may be crashing into the differential when shifting from 2WD to 4WD. The spacer allows just enough clearance for smooth shifting.
Try loosening the three bolts on the actuator by one full turn and see if it changes anything.

Loosen the actuator from the differential (about two full turns for the bolts) and try shifting. If you can lock in, you will need our actuator spacer.

It is powered by the orange wire coming off the tank lever (plugs into where the OEM actuator gets unplugged). Double-check the connection.
Check the micro switches inside the tank lever. Sometimes the metal on the switch needs to be bent slightly in order for the cable clasp to activate the switch.
Test the connector to see if power is making its way to the orange wire.

This is most likely a cable adjustment issue. Watch the adjustment tips video. Ensure all connections are tightly secured and that the wires are connected correctly. If the issue persists, the sensors inside the differential may be bad.
Use a multimeter to test:
In 2WD, the bottom sensor should be shorted to ground.
In 4WD, the middle sensor should be shorted to ground.
In Diff Lock, the top sensor should be shorted to ground.

First, check cable adjustment and wiring. The diff lock light should turn on when in diff lock. Try turning the machine on/off to see if anything changes.
If the light still doesn’t turn on:
Move the wheels a bit and try again by riding a few feet.
Plug the OEM #3 wire back into the top position of the diff.
Shift into diff lock and see if the OEM diff lock light appears on the dash.
If the OEM light doesn’t display, the diff lock sensor may be bad.

The actuator is designed to allow some diff oil to enter to keep it lubricated, but it shouldn’t be leaking excessively.
Check the following:
Ensure your vent tube is clean and clear.
A clogged vent tube can build pressure in the diff, forcing oil out.
Check if your diff fluid is overfilled.Inspect the small o-ring supplied with your kit; if it’s damaged or missing, it could cause a leak where the cable enters the actuator.
If everything appears normal, apply RTV sealant around the housing where the cable enters to prevent further leaking.If you have bellows, ensure they are not too small, as this can cause pressure buildup.

Look behind the actuator for the pin and ensure it is sitting flush.

This may be related to the speed limit bypass. Check the connections and ensure proper installation.

Run power to the accessory, then cut one of the wires and tie it into our connector.
Example: If installing a light bar, run a positive and negative wire to the light bar (which will turn it on all the time). Then cut the negative wire, take those two ends, and connect them to our connector. Now, when you push the 4WD button, it will close those wires back together.

Double-check the cable adjustment. Try turning the wheels while shifting.

Make sure you have the display lights upgrade kit.

Refer to the “How to get into diff lock with your Sure 4 Manual kit.”

If the ball at the end of the cable came out, Joe made a bracket to replace the washer, covering where the cable goes in.

Unplug the white wire/blade and test.

The white wire provides power to that light. Check that connection and make sure nothing is loose or frayed.

Some vehicles (especially those with lid-snap-on kits) have connectors in different locations than the installation video.
There should be either 1 wire coming off of the differential where our kit would plug in OR 2 wires coming off the front hubs with the appropriate connectors.
If nothing comes off the diff, go to the hubs, follow the wires coming off of them, and you should then find where to plug in our connector.

Is their OEM switch still plugged into 2WD?
Is the fuse in our wire harness good/bad?
Check all wires/connections. Something may have been bumped loose during installation.
Check if the resistor is plugged in.
Try unplugging our kit and see if the light goes off.
Disconnect all connectors, including those going to the battery, and reconnect them.
The best way to determine whether our kit is faulty is to plug the diff back into the OEM connector and see if the check engine light goes away.