Safety Functions
By way of plausibility checks and checking the line connections for shorts or opens, the control unit can detect and store defects.
In the event of failure of the transmission control or when defects are detected which lead to critical driving situations (for example: impermissible downshift), the mechanical emergency program is activated (transmission control unit is switched off and failure indicator activated.) A self-test of the entire safety hardware takes place during each new start.
The vehicle can only be driven with restrictions in the mechanical emergency program (only the 3rd, 4th gears and reverse can be shifted.) In this case, 3rd gear is engaged in selector lever position "2" and "1", 4th gear in position "0" and "3" and reverse in position "R". The main pressure assumes its maximum value. Reverse lock and shift-lock, if installed, of the selector lever are not active.
Downshifts engaged manually at a speed which is too high are generally not performed.
The R-lock (reverse lock-out) prevents reverse being shifted hydraulically at a speed above approximately 5 MPH.