Freelander System Description and Operation
AUTOMATIC GEARBOX - JATCO
44-46
DESCRIPTION AND OPERATION
Engine Cooling Fan
If the gearbox fluid temperature increases to 110
°
C (230
°
F), the EAT ECU sends a cooling request message to the
ECM on the CAN bus. The ECM then switches the engine cooling fan on, or if it is already on, keeps it on, to maintain
the air flow through the fluid cooler.
The EAT ECU cancels the cooling request when the fluid temperature decreases to 100
°
C (212
°
F).
Diagnostics
If the EAT ECU detects a failure in an associated component, a fault code will be stored in the EAT ECU memory.
TestBook/T4 is used to retrieve these fault codes to identify the cause of the failure.
Gearbox Fault Status
If the EAT ECU detects a fault with the gearbox system it will enter a fail safe mode. There are many fail safe modes
the EAT ECU can adopt.
The EAT ECU will adopt the fail safe mode most acceptable for the driver and will ensure the least amount of damage
to the gearbox.
When a fault is detected a CAN message is sent from the EAT ECU to the instrument pack and the MIL will be
illuminated if the fault is related to OBD. If the ECU is able to implement a limp home mode, the instrument pack LCD
will display '4' and 'F' alternately as the gearbox status display. Some faults may not display '4' and 'F' in the instrument
pack, but the driver may notice a reduction in shift quality.
Engine Speed and Throttle Monitoring
The ECM constantly supplies the EAT ECU with information on engine speed and throttle angle through messages
on the CAN bus. This information is used by the EAT ECU to calculate the correct timing of gear changes.
If the messages are not received from the ECM, the EAT ECU will implement a back-up strategy to protect the
gearbox from damage, whilst allowing the vehicle to be driven.
In the event of an engine speed signal failure any of the following symptoms may be observed:
l
Decrease in fuel economy
l
Increase in engine emissions.
In the event of a throttle position signal failure, any of the following symptoms may be observed:
l
Harsh gear changes
l
No kickdown
l
Torque reduction request inhibited.
