MG MG6 Series 2011 Service Manual page 314

Engine
• Handset transponder.
• Transponder coil.
• PARK/NEUTRAL switch (automatic transmission only).
•
The description here relates solely to the functions
concerning the ECM, for further information SECURITY
AND LOCKING, Security System Arming and Disarming.
The handset contains a coded transponder chip which
communicates with a transponder coil fitted around the
handset docking station. When the handset is moved to the
CRANK position, the immobilisation module communicates
with the coded transponder chip using a code known only
to that vehicle's transponder. If the transponder recognises
the code it will transmit it to the immobilisation module. If
the number matches the code stored in the immobilisation
module, it will allow the engine to be started, if the
transmission must be in PARK or NEUTRAL (automatic
transmission only).
When the handset is docked, it receives a new code from the
immobilisation module. This code must be received on the
next ignition cycle to allow the engine to start. This is known
as a 'rolling code'.
In production, the immobilisation module is programmed with
a code specific to that particular vehicle. When theECM
is fitted it is not coded but has to 'learn' the code from
the immobilisation module. The immobilisation module and
the ECM then function as a matched pair. An ECMcannot
function without being connected to the immobilisation
module. TheECM then cannot be fitted to any other vehicle.
In serviceECM are supplied uncoded and must learn the code
stored in the immobilisation module using the procedure in
the diagnostic tool. A replacement immobilisation module
is supplied coded to that vehicle and once fitted the rolling
codes must be synchronised to the ECM.
When a correctly coded handset is used to attempt an engine
start, the immobilisation module will energise the starter relay,
located in the engine compartment fusebox, and crank the
engine. The immobilisation module will also authorise engine
fuelling by transmitting a signal to the ECM.
The security code and authorisation to start are transmitted
between the immobilisation module and theECM via the CAN
Bus.
CAN Bus Data Received By The ECM From The
TCM
ECM The ECM receives the following information from the
TCM via the CAN Bus:
• Target gear.
Version 2.0
Engine Fuel & Management System
This tells theECM what gear is currently engaged or, if a
gear change is in progress, the gear to which the EAT is
shifting. This information is used by theECM to assist in
engine load change prediction.
• EAT status.
This signal is used to inform theECM that there is a
fault with the EAT that increases emissions above an
unacceptable limit.
• TCM torque level required.
This message is used to request engine torque reductions
from the ECM. This is equivalent to lifting off the throttle
in manual vehicles.
• EAT cooling request.
This signal is used to inform theECM to switch on the
cooling fan. This signal will only be set when the EAT
fluid temperature becomes high.
CAN Bus Data Sent From The ECM To The TCM
The TCM receives the following information from the via the
CAN Bus:ECM via the CAN Bus:
• Handset dock status.
This signal is transmitted from the ECM. The TCM
is powered via the main relay. When the handset is
removed, it identifies the change in state. The TCM
remains powered to allow fault data to be stored.
• Engine speed signal error.
This signal, sent from the ECM, informs the TCM that
there is a fault with the value of engine speed that it is
calculating. The TCM can then take the necessary steps
to compensate for this error and protect the EAT from
damage.
• Torque reduction status.
This message is transmitted from theECM and is used
to inform the TCM of the success of a torque reduction
request.
• Torque measurement error.
This signal is used to inform the TCM that the torque
values it is receiving from theECM are incorrect/faulty.
• Engine speed.
The TCM uses the engine speed to assist in gear shift
scheduling.
• Actual engine torque.
TheECM produces this parameter. This signal indicates
the actual engine torque produced at any moment. The
TCM uses this parameter to control gear shift scheduling.
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