Troubleshooting — General Information (Mercedes-Benz S-Class W140)

If you detect a fault with your automatic transmission, first check the ATF level (see Chapter Routine maintenance). If the level is insufficient, check the condition of the corresponding seals. Carefully inspect all 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 transmission. Before replacing any sensor, read the fault codes from the control unit memory.

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