since buying my l405 2013 4.4 autobiography the passenger auto step comes out less and less, no problem with driver step, any idea whats causing the problem

Simply dirt crud and probably rust on the pivot points in the brackets but also importantly on the drive shaft in/from the motor. They have a relatively weak torque threshold for stopping working (safety device if obstructions encountered) so it doesn't take much crud to trigger the sensor and stop. Requires regular cleaning and greasing at the critical points - simple as. Mike - MPx

2017 5.0 V8 Supercharged SVAutobigraphy Dynamic SVO Palette Grey (2021-...)
2012 5.0 V8 Supercharged Autoboigraphy Orkney Grey (2017-2021)
2007 4.2 V8 Supercharged Vogue SE Tonga Green (2012-2017)
2002 4.4 V8 Vogue Bonnatti Grey (2008-2012)

Hi Andy, welcome to FFRR.com,

Use the SEARCH facility above for term “deployable steps” -loads of info on this very common issue, and how to fix, -temporarily. I’m afraid it’s an ongoing maintenance issue!

 “If it ain’t broke, don’t fix it” -where’s the fun in that?