98 ml320 can't unlock from inside
 

just purchased this vehicle. The lock switch on the center console will lock all doors but won't unlock any.

Could this possibly be aam option #20-Central Lock CL-dual stage?

Also can anyone direct me to a pdf or other online resource for an owner's manual?

THANKS

Most likely the switch itself is the problem...but as with any computer controlled system the real diagnosis would be with a scanner that can look at live data stream in the AAM.