Possible reasons for the loss of all automatic transmission gears on a Mercedes:
1. Low transmission fluid (ATF):
* Check the ATF level and add fluid if necessary.
*Low fluid levels can cause overheating and damage to the transmission.
2. Damage or contamination of ATF:
* Dirty or old ATF can cause clogged and sticking transmission valves.
* Replace ATF and flush transmission system.
3. Malfunction of solenoids or sensors:
* Solenoids control ATF flow and gear shifting.
* Sensors provide information about engine speed, vehicle speed and gear shift position.
* Check solenoids and sensors for faults.
4. Malfunction of the electronic control unit (ECU):
* The ECU controls the transmission by receiving signals from sensors.
* A malfunction of the ECU may result in incorrect operation of the transmission.
5. Mechanical problems:
* Wear on internal transmission components such as clutches, clutches and planetary gears can cause gear loss.
*Transmission mechanical repair or replacement is required.
6. Faulty wiring or connections:
* Damaged or loose wiring may cause the transmission control system to malfunction.
* Check wires and connectors for damage.
7. Limp Home Mode:
*In the event of a serious problem, the transmission may go into limp mode.
* In this mode, only one gear is available (usually 3rd or 4th).
Diagnostic recommendations:
* Check ATF level and condition.
* Read trouble codes using an OBD-II scanner.
* Conduct a visual inspection of wiring and connectors.
* Determine if there are faults in the ECU, solenoids and sensors.
* Consider mechanical repair if other causes have been ruled out.