Vehicle: 2010 Mercedes Benz E 550 4MATIC Sedan, 5.5L V-8, Automatic Transmission
Problem: The shifter goes into “Park” while driving under 12 miles per hour. There were no DTCs.
Details: The tech found that, while monitoring the check park request PID from the TCM, a park request was being received when the problem occurred. This meant that the park assist module was requesting the transmission to shift into park. The module that sends that signal to the park assist module was the radar sensor control (RSC) module.
The tech unplugged the RSC module to see if that fixed the problem. It did, so he checked the module for corrosion or water intrusion. It checked out good.
Next, he tested all the electrical circuits and found that, when the problem occurred, reference voltage from the RSC module to the radar sensors dropped from 8 volts to 2 volts. He unplugged the radar sensor and found the two middle sensors were shorting the reference voltage from the RSC module.
Confirmed Repair: He replaced the two center radar sensors and the problem was fixed!