Mercedes-Benz W212 automatic jumps into P while driving
Why does the W212 automatic jump into P by itself while driving?
Most often the cause is a fault in the electronic ignition lock: the key recognition does not work properly and the automatic P function engages. The symptom usually appears at creeping speed or at traffic lights.
How does the fault show up and how can it be recognised?
The transmission engages P at walking speed, and a clicking sound may be heard as the parking lock pawl bounces over the teeth. The fault may show as fault codes with the diagnostic tool, and the symptom is more sensitive in warm weather than in winter.
How is the fault repaired?
The common repair is replacing or repairing the ignition lock, and for many the symptom has disappeared afterwards. For some the fault continued, so it is worth reading the fault codes and checking other possible causes, such as the speed sensor. Leave the ignition lock replacement and the necessary settings to a workshop.