Mercedes-Benz W220 automatic transmission in limp mode (722.6)
W220 automatic transmission goes into limp mode, what causes it?
In limp mode usually only 1st and 2nd gear and reverse work. Typical causes are a fault in the conductor plate inside the transmission or its speed sensor, a damaged connector or the gear selector module connector. The cause is found from the fault codes, which a workshop diagnostic tool reads.
Can an ABS sensor fault affect the W220 automatic transmission?
Yes. If the ABS sensor gives no speed signal, the transmission can start behaving oddly and the instrument cluster act strangely. Sensor data and fault codes can be seen with a diagnostic tool, so read the codes before replacing parts.
Why does replacing the transmission control unit not always fix the W220 fault?
The control unit must match the car's original version and ratio, and a unit from another engine type does not work directly. The control unit connector's sleeve and sealing ring can also leak oil into the unit, in which case the fault is fixed by replacing the sleeve and ring.