Diagnostics

DIAGNOSTICS
While the ignition is on, the EAT ECU diagnoses the system for faults. The extent of the diagnostic capability at any particular time depends on the prevailing operating conditions, e.g. it is not possible to check torque converter lock-up while the vehicle is stationary, or to check for a short circuit to earth if the circuit concerned is already at a low potential.

If a fault is detected, the EAT ECU immediately stores a fault code and the values of three operating parameters associated with the fault. Depending on the fault, there are four possible effects:
^ The fault has little effect on gearbox operation or vehicle emissions. The driver will probably not notice any change and the warning lamps remain extinguished.
^ All gears are available but kickdown does not function. 'GEARBOX FAULT' will be displayed on the instrument pack message center. The MIL remains extinguished.
^ Limp home mode is selected and vehicle performance is greatly reduced. 'GEARBOX FAULT' will be displayed on the instrument pack message center. If the fault is detected on a second consecutive drive cycle, the MIL illuminates.

The fault codes can be accessed using Test Book. On vehicles up to 99MY the automatic transmission fault codes are a numeric code recognized by Test Book. On V8 vehicles from 99MY the automatic transmission fault codes are both numeric and OBDII 'P' codes recognized by Test Book and other suitable scan tools.

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.