Test Harnesses

Retired BLM Rig products
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Retired BLM Rig
Posts: 1138
Joined: Sun Jan 31, 2016 6:51 pm
Model Year: 2008
Location: State of Jefferson

Test Harnesses

Post by Retired BLM Rig » Thu Jul 20, 2023 1:40 am

If you're having problems with your lockers and you can't figure out if it's the SmartBar or the locker actuators inside the axle housing, I have put together a couple test harnesses I can mail out to help with your diagnosis. Just plug the test harness into the front or rear axle locker connector and then connect it to a 12V battery so you can confirm if the actuators are capable of locking. Jack up the axle, spin the tire, then connect the battery and spin the tire again, it should lock right away. On the front axle of a 2014-2018 truck, you'll need to have the truck in 4H or 4L when you do the test, so the Center Axle Disconnect (CAD) on the passenger side axle is engaged. Otherwise, you might think that it's not locking when actually it is. All I ask is that you mail the test harness back to me when you're done, so they're available for the next guy that needs to test his truck.

This will help you determine if the problem is with a defective locker actuator inside the axle housing or the Final Drive Control Module (FDCM) AKA the SmartBar/front sway bar that controls the lockers. You can also unplug the FDCM and check for corrosion on the pins. I've seen moisture get inside on the circuitboard and cause all kinds of problems, including random locking when the switch is in the "Unlock" position or failure to lock with flashing indicator lights. Corrosion on the pins is your first indicator that there's moisture inside the SmartBar.

Also remember to check your sensor magnet that mount right next to the locker actuator. They can get loaded with fine metal particles that changes the air gap between the magnet and the sensor, which can cause flashing indicator lights and failure to lock.

If you determine that the axle actuators are good and that your problem is with the FDCM, my "Full SmartBar Bypass" will restore the proper function of your lockers and sway bar disconnect. It replaces all the electronics, except for the locker actuators inside each axle housing and the factory dash switch. My module mounts under the dash, so it's not exposed to all the harsh elements like the FDCM is. It retains the full function of the factory dash switch and works in any transfer case range.

Email me your mailing address and I'll send the test harness ASAP.


Posts: 5460
Joined: Thu May 24, 2012 4:23 pm
Model Year: 2008
Location: Brownsville Pa.

Re: Test Harnesses

Post by RustyPW » Thu Jul 20, 2023 4:55 am

PWOC #53

My build thread. http://forum.powerwagonregistry.org/vie ... =13&t=2826 :cash: :cash:

Moab '09, '10, '12, '14, '20, '22
Rausch Creek - Summer '10, Spring-Fall '11, Spring '12, Summer '13, Summer '14, Summer '15, Summer '16, Summer '17, Summer '18, Summer '20, Summer '22, Summer '23, Summer '24,
AOAA Summer '19.

NRA - Benefactor, Golden Eagle. :lockedandloaded:

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