Limp home mode

The TCM software contains functions which take control of the transmission if serious faults occur.

The fault characteristic decides which strategies are to be used.

The vehicle remains capable of restricted operation, unless there is a fault in the TCM itself or at the TR sensor.

NOTE: If the TCM sensor is defective, both clutches are disengaged and it is no longer possible to continue driving. In the event of failure of the TR sensor, it is no longer possible to start the vehicle, or the transmission is fixed in the N position, as a result of which it is impossible to continue driving.

Different measures are implemented depending on the current gear position and driving situation when the fault occurs:

In the event of failure of an electric motor which actuates the lever actuator of the clutch, the TCM will only actuate the electric motor which is intact. If, for example, electric motor 1 has failed, then this path through the transmission is blocked (1st, 3rd and 5th gear). The TCM then only actuates electric motor 2. This actuates the clutch of reverse, 2nd, 4th and 6th gear via the lever actuator.
In the event of failure of the gearshift system or the rotational speed sensors, the fault reactions of the system range from the blocking of individual gears or the blocking of an entire path through the transmission (even/odd gears) to only permitting the vehicle to be driven in the currently engaged gear.
In limp home mode, a text message is displayed in the instrument cluster and/or the MIL and/or the transmission warning light comes on (depending on the fault type).

When the engine is started again (ignition switched off for approximately 15 seconds), a self-test is performed in order to check whether there are any faults in the system. If the fault is still present, limp home mode is reactivated. If the fault is no longer present then it is no longer displayed on the instrument cluster and the MIL and/or the transmission control light will be off. However, the fault remains stored in the TCM.

In the event of a fault, it is recommended to continue driving so long as it is necessary and to look for the nearest workshop or to park the vehicle in a safe location.