Location of automatic transmission overload sensor in Mercedes 124
The automatic transmission overload sensor is located on the left side of the gearbox housing, next to the kick-down cable.
Appearance and marking of the sensor
The sensor is a small metal cylinder with an electrical connector.
Sensor marking:
* A 170 540 01 17
Sensor function
The overload sensor (also known as the underdrive switch) monitors the load on the transmission. When the load on the transmission becomes too great, the sensor is activated and sends a signal to the electronic control unit (ECU), which causes the transmission to downshift.
This helps protect the transmission from damage caused by excessive torque or towing heavy loads.
Signs of a faulty automatic transmission overload sensor
A faulty overload sensor can result in the following symptoms:
* Difficulty downshifting
*Excessive downshifting
* Gearbox slipping
*Loss of power when accelerating
*Transmission related fault codes
Replacing the automatic transmission overload sensor
To replace the automatic transmission overload sensor, perform the following steps:
1. Disconnect the negative terminal of the battery.
2. Remove the air filter and air filter housing.
3. Disconnect the connector from the overload sensor.
4. Unscrew the sensor using a 12mm wrench.
5. Screw in the new sensor, tightening it to a torque of 20 Nm.
6. Connect the connector to the new sensor.
7. Install the air filter housing and air filter.
8. Connect the negative terminal of the battery.
Note: Clean the transmission housing surface around the sensor before installing a new sensor to prevent contamination.