How to: Jeep TJ/LJ Rubicon Locker Actuator troubleshooting

Is nothing happening when you push the locker button on your 2003-2006 Jeep TJ or LJ Rubicon? Is one or both of the locker dash indicator lights just blinking? You have come to the right place to help you do the basic troubleshooting and repair the issue. Remember that none of the basics are complicated and now is a great time to learn, but it is always ok to consult a pro if you decide it is a bigger project than you want to handle. If things get into having to remove the locker assembly in the differential, that is well past the basics of this fix. Common Failures include air pumps failing due to wear and tear, and air hose fittings may become brittle or rusty and crack over time. Troubleshooting can be a bit of a rabbit hole but here are the steps that I suggest.

1. Understand the System

03-06 Rubicon lockers use a low-pressure air pump to engage the lockers. If the locker is not engaging, it may be a problem with the pump, wiring, air hoses, or the locker itself. It also can be something as simple as operator error. Don’t worry, we all have been there.

2. Check Basic Operations

Unless you have (or a previous owner) have made modifications the Jeep must be in 4-Low. Start simple, make sure your Jeep is in 4WD low-range. The lockers will not engage unless the vehicle is in 4-Low by default.

One push down on the switch will engage the rear. A second push down on the switch will engage the front. Note that to fully lock the jeep needs to be moving a bit to get the locker to engage once pressurized. Sometimes to get the front to lock, some side-to-side steering wheel turns can help.

Note whether the indicator light on the dash is blinking (trying to engage) or does not illuminate at all.

3. Inspect the Air Pump

The OEM location for the locker air pump is on the driver’s side rear of the transfer case.

First, when you press the locker button (and the transfer case is in 4 low, and the ignition is on) listen for the pump: When you press the locker button, you should hear the air pump activate. If not, the pump may not be receiving power or could be faulty. Pro tip: you do not have to have the engine on for the key ignition to be on which makes it easier to hear the pump run.

If you hear the pump run, but it does not shut off, or it pulses, most likely you have a leak in the air system downstream of the pump.

If you do not hear the pump run, more than likely you have an electrical failure, malfunction of some type, or an air pump failure. If you do not hear the pump run, start there and focus on getting the pump to run. Nothing else will matter if the pump is not running.

4. If the pump runs and does not shut off or surges, examine the air hoses and fittings for leaks

Follow the air hoses from the pump to the axle housings (front and rear). Look for cracks, kinks, or disconnections in the lines. Any air leak will prevent the lockers from engaging.

Air leaks can happen in the rubber hoses that run from the pump to the differentials, the differential pass-through fitting that connects the external locker air hose to the internal air hose, or the internal hose that comes from the pass-through fitting to the locking mechanism in the differential.

I have seen the fittings that our solution replaced, intact enough to look like they are visually ok, but have pinhole leaks that do not allow the locker to function.

Inspect your fittings closely. Some of the fittings I have replaced are clearly broken. Both were leaking and why the locker was not working.

Our differential pass through fitting solution can be found along with our air hose repair kit can be found at https://www.obsoletejeep.com/shop

5. If the pump does not run diagnose the pump and associated electrical systems

Again, always start simple. Check the fuse, battery, and switch.

Inspect electrical connections on the pump, switch, fuses, and relays. Ensure the wiring to the pump is secure and is not damaged.

Remove the switch from the dash and use a multimeter to test the switch for continuity. As of January 2025, OEM replacement switches are still available from Mopar. The part number is 56047066AC Switch-Axle Lock.

If you determine that the pump has failed, the fun starts as the OEM pump is no longer available. This was Mopar Part# 5127836AA. At this time our best recommendation is to spend some time doing research as there are folks who have made Kia Sorento Part 510303E100 work and a few websites that sell the pump if they have them in stock.

6. Other Failures

While rare, the locker mechanism can wear out or break, especially if the Jeep has seen heavy off-road use. Ring gears, pinion gears, and axle shafts can break which will not allow a locker to function correctly. Debris or water in the airlines or differential housing can cause the lockers to not function. If you are at this point, you are past the simple fixes outlined here, but the great thing is, stealing a line from a college professor that I am a huge fan of, “everything is figureoutable”.