Fault effects and warning indications (Automatic gearbox - ZF4HP22/24)

After the detection of a fault, the effects remain active for the remainder of the drive cycle. In subsequent drive cycles, as soon as the EAT ECU diagnoses the fault is no longer present, it resumes normal control of the gearbox. The conditions required to diagnose that the fault is no longer present depend on the fault. Some faults require the engine to be started, others require only that the ignition is switched on.

After a fault has not recurred for forty warm-up cycles, the fault is deleted from the EAT ECU memory. Only five different faults can be stored in the memory at any one time. If a further fault occurs, the fault with the lowest priority will be replaced by the new fault.

Mechanical limp home In the mechanical limp home mode, gear engagement is controlled by the manual valve. The gearbox is fixed in 4th gear if the fault occurs while the vehicle is moving, or 3rd gear if the fault occurs while the vehicle is stationary. 3rd gear is also engaged if a vehicle is brought to a stop and the selector lever is moved out of, and back into, D. Neutral and reverse gear are also available.

Fault effects and warning indications