Troubleshooting — General Information (Mercedes-Benz S-Class W220)

If you detect a fault with your automatic transmission, first check the fluid level (refer to Section Checking the Automatic Transmission Oil Level). If the level is insufficient, check all the seals. Carefully inspect all the hoses related to the transmission fluid, as well as the cooler, and make sure there are no signs of leaks. The only thing you can do yourself is to check and, if necessary, replace the sensors related to the operation of the box (temperature and revolutions). Before replacing any sensor, read the fault codes from the control unit memory.

In case of a relatively serious breakdown, the transmission control system will switch to a safe mode of operation, while entering the corresponding code (or codes) into the control unit memory. The codes can be read using special equipment.

If there is none, determine the nature of the malfunction (electrical or mechanical).

Do not attempt to remove the transmission, as diagnostics can only be performed on the transmission installed on the engine.