Mechanical Emergency Program

The following applies in the event of total failure of the transmission control:

• No interruption in power transfer while driving forward (no gear changes)
• When the vehicle is stationary and "engine off": the parking lock will be engaged

The transmission electronics may still be in operation during the mechanical emergency program, communication may also still be possible but the power supply to the actuators (MV and EDS) is deactivated. The hydraulic system of the gearbox is designed so that restricted operation is still possible.

It is not possible to reselect a drive position with the selector lever. This means the vehicle can only be driven forward within certain restrictions until the engine is switched off. A drive position can not be engaged after turning the ignition off and restarting the engine  .

Vehicle safety is ensured because the parking lock engages when it is depressurized. As soon as the pressure in the parking lock cylinder drops the parking lock system is pretensioned mechanically (operating lever spring). The mechanical parking lock will not engage at speeds > 5 km/h. Once engaged, the parking lock can only be released with the mechanical emergency release  .

When the mechanical emergency program occurs:

• While driving forward, it is still possible to continue driving in 3rd/5th gear (3rd gear when 1st, 2nd or 3rd gear was previously engaged, 5th gear when 4th, 5th or 6th gear was engaged). This is interrupted by turning off the engine, the parking lock will engage once the hydraulic pressure has dropped.
• While in reverse, the gearbox assumes the neutral position and the parking lock is engaged (< 5 km/h).
• While in hydraulic neutral, the parking lock will engage (< 5km/h).
• In position P, the gearbox remains in this status and the parking lock remains engaged.

The driver is informed of the different emergency situations by the Check Control messages.