Tested SLS system....Held idle at 2k rpm with 230lbs loaded in the rear. Used a tape measure, and there was no change in height.
Fluid level is good, and has been for a number of years, so no leaks.

So its definitely not working....what's the next item to check?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k