Description and Operation of the Range Rover P38 Automatic Gearbox
44
AUTOMATIC GEARBOX
NEW RANGE ROVER
26
DESCRIPTION AND OPERATION
The fault codes can be accessed using TestBook. On
vehicles up to 99MY the automatic transmission fault
codes are a numeric code recognised by TestBook.
On V8 vehicles from 99MY the automatic transmission
fault codes are both numeric and OBDII ’P’ codes
recognised by TestBook and other suitable scantools.
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 in high range,
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.
In the mechanical limp home mode in low range,
depending on the severity of the fault, the engaged
gear is held until the vehicle is brought to a stop. The
gearbox then selects and holds 3rd gear.
Calibration Selection
EAT ECU’s differ between NAS, UK/Europe and ROW
markets and are identified by differentiation between
the part numbers.
On V8 vehicles from 99MY, the ECU contains two
calibrations for 4.0 and 4.6 litre engines. When a
replacement ECU is fitted, the correct ECU calibration
must be selected or the ECU will store a gearbox fault
and ’GEARBOX FAULT’ will be displayed in the
message centre. The vehicle can still be driven and is
not in ’limp home mode’.
Removed EAT ECU’s remember their calibration
setting and if re-fitted to the same vehicle will not
require calibration. A new EAT ECU will require
calibration using TestBook.
If an ECU is fitted from another vehicle, the message
centre will not display the ’GEARBOX FAULT’
message. The correct calibration level must be
selected or premature gearbox failure will occur.