Are you able to read the codes off the DTC? It'll give you a great place to start troubleshooting. If the steering rack needs to be replaced, take a look at the link below for our guide on a DIY fix.

Mercedes-Benz W211 Steering Rack Replacement (2003-2009) E320, E500, E55 | Pelican Parts DIY Maintenance Article


-Dmitry

seems like intermediate shaft stiction noise, on japanese and usual american cars I remove the ISS and grease it with very thin teflon grease. Usually available at toyota, mazda/ford and chevy dealers.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)