Are your rear bags original?

Before replacing them I would verify by a leak test that they aren't leaking. If the ride height is not dropping overnight, the bags are probably fine in the rear.

You need non-sport bags for the 4.8iS because of the articulation of the EHCII system, you can get replacements from Arnott Industries in the states with a lifetime warrantied for $200 plus shipping.

Check the linkage on the rear sensor arm to be sure it is not broken, or frozen rusted stuck in place. If it is good, then I would verify the linkage on the sensor arm is good, as well as no leaks on the rear bags (you can almost tell visually).

If you have no issues there, you are not throwing ride height sensor faults, so I would say your issue is the module.

Did you run a ride height re-calibration after clearing the module of faults?

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards