On the facelift, if its the corner sensors they are a right angle sensor (not straight like the other 6), and you'll have to drop the bumper for them.

On my pre-facelift I had a dead sensor in front middle and rear middle and they were able to be R&R'ed without removing bumper, from the backside

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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