MG MG6 Series 2011 Service Manual page 313

Engine Fuel & Management System
Cooling Fan Relay Unit
The cooling fan relay unit is fitted to the LH side of the radiator
and is fitted with two relays.
The cooling fan is operated by the relay unit under the control
of the ECM. TheECM uses information provided by theECT
sensor,BCM and theA/C pressure switch to limit engine
coolant temperature.
The fan strategy includes an engine idle adjustment to
compensate for the additional load when switching on the fan.
The cooling fan may run for a period of 5 minutes after the
handset is removed to provide engine compartment cooling
in hot conditions.
Main Relay
The main relay is located in relay position 4 in the engine
compartment fusebox. It is a four pin relay using the DIN pin
layout. The relay does not include a reverse polarity protection
diode as this function is carried out by the ECM. The relay coil
has a resistance of 80Ω ± 25% and is controlled by the ECM.
Fuel Pump Relay
The fuel pump relay is located in BCM. It is a four pin relay
using the DIN pin layout. The relay does not include a reverse
polarity protection device. The relay winding has a resistance
of 80Ω ± 25%.
The relay is controlled by theECM and, when energised,
supplies battery voltage to the fuel pump circuit under the
following conditions:
• The ignition is on (for a duration of 2 seconds)
• Engine cranking/running
5 Speed Electronic Automatic Transmission (EAT)
The 5 speed EAT has a separate Transmission Control Unit
TCM which manages the functions and diagnostics relating to
the transmission unit. TheTCM makes use of various inputs to
control the mechanical parts of the EAT via solenoid operated
oil control valves. This description is limited to only the inputs
Version 2.0
and outputs which relate to the ECM. For further information
on the EAT refer to Automatic Transmission.
TheECM and theTCM are able to communicate via the CAN
Bus. This allows the sharing of information collected from
sensors installed in the powertrain components. TheECM
transmits sensor information which is used by theTCM
to control gear shift timing and ratio selection. TheTCM
transmits information which is used by theECM to control
engine torque output and cooling fan operation.
On-Board DiagnosticsOBD
The EMS has been designed to meet the current exhaust
emissions standards, European Commission Directive Stage 4
(EUCD 4). OBD is concerned with the monitoring of certain
engine functions, the failure of which would lead to an increase
in emissions above legislated thresholds. OBD concentrates
mainly on the engine management system, but other systems,
such as automatic transmission and anti-lock braking may also
be monitored. When such a fault occurs it is stored as a code
in the memory of the ECM, or relevant ECU.
The EMS warns the driver of malfunctions by illumination of
the Malfunction Indicator Light (MIL). The post catalyst HO2S,
positioned downstream of the TWC, monitors the operating
efficiency of the TWC.
The OBD function runs in the background within the
operations managed by the ECM. The systems which fall
within the scope of OBD are monitored when the vehicle
is in use, the driver will not be aware that any 'testing' is
being carried out. The individual system tests take place as
the correct circumstances occur, the full range of driving
conditions necessary to accommodate all the OBD tests is
known as an 'OBD drive cycle'. Faults logged by theECM are
normally qualified by one of the following failure types:
• MIN. the minimum expected value has been exceeded
• MAX. the maximum expected value has been exceeded
• SIGNAL. the signal is not present
• PLAUS. an implausible condition has been detected
The nature of the fault is indicated by codes assigned to
particular conditions or components.
stored in theECM memory, these can be retrieved using the
diagnostic tool.
Engine Immobilisation
The engine immobilisation system prevents unauthorised
starting of the engine, i.e. without a correctly coded handset.
The system consists primarily of the following components:
• ECM
• ESCL
• Body Controller ModuleBCM
Engine
Fault codes will be
297