The FSM has a diagnostic procedure for the ACC. It only requires a multimeter.

Yours should be new enough to have self diagnosis. It gives blink codes to tell you what's wrong. For that you will need to have an impulse counter. It is an LED, push button, and resistor with some test leads.

The procedure calls for a special breakout box that plugs into the 2 big plugs behind the PBU but you can read between the lines in the procedure and figure out which pins on the 2 connectors go to whichever sensor or actuator the test is calling for.

If you suspect a sensor, grab the ETM schematic and ohm them out from the PBU plugs.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech