Mercedes-Benz W204 722.9 automatic jerking and limp mode: conductor plate and KYB valve
W204 722.9 automatic jerks or goes into limp mode, is the cause the conductor plate or the KYB valve?
The cause varies. Often the fault is in the conductor plate, i.e. the transmission's electrical connection, and second most commonly in the transmission oil. The KYB valve rarely causes limp mode. A fault in the transmission control unit is also often linked to limp mode.
What should be checked on a W204 automatic before taking the transmission apart?
First see whether there is oil in the connector of the transmission control unit. Oil can run from the transmission connector along the cable into the electronics, so the connector and the electronics are cleaned with electronics cleaner. A solenoid test alone does not tell whether a valve is stuck.
Do adaptations need to be done after replacing the conductor plate or the KYB valve?
There is no consensus on this. On the five-speed transmission a new conductor plate did not need programming. On the seven-speed, it is worth resetting the adaptations and letting the transmission learn the new values, which can take a long time. Also check the oil level after the replacement.