Troubleshooting — General Information (Mercedes-Benz M-Class W163)

If you detect a fault with your automatic transmission, first check the ATF level (see Chapter Replacement and checking of ATF level, replacement of AT filter). If the level is insufficient, check the condition of the corresponding seals. Carefully inspect all ATF hoses, as well as the transmission fluid cooler, and make sure there are no signs of leaks developing. The only thing that can still be done by the vehicle owner is checking/replacing the information sensors of the AT control system - before starting to replace the suspected sensor, query the control module memory - all significant failures are recorded in the module memory as DTC codes, and in especially serious cases, the TCM automatically switches the AT to emergency operation mode. DTC codes are read using special diagnostic equipment connected to the on-board diagnostic system (DTC) connector (see Chapter Engine electrical systems). If there is no access to the necessary devices, it will be enough to try to at least qualitatively determine the nature of the failure (at level: electrical/mechanical) in order to facilitate communication with car service specialists. You should not start removing the AT prematurely, since its diagnostics are only possible in the installed position.

[Original source of information: mercedesman]