Page 27 of 37
27
OUTPUT CONTROL FUNCTIONS
FUEL PUMP RELAY CONTROL
ME 7.2 controls the fuel pump relay as with previous systems with regard to engine speed
input for continual activation of the relay.
The ME 7.2 will switch off the fuel pump relay when an airbag is activated as an addition-
al safety function. The signal is passed from the MRS III control module to the ME 7.2 over
the CAN line
E BOX FAN CONTROL
The E Box fan is controlled by ME 7.2. The control module
contains an integral NTC temperature sensor for the pur-
pose of monitoring the E box temperature and activating the
fan.
When the temperature in the E-Box exceeds predetermined
values, ME 7.2 provides a switched ground for the E Box fan
to cool the E box located control modules.
With every engine start-up, ME 7.2 briefly activates the fan
ensuring continued fan motor operation for the service life of
the vehicle. This feature is intended to prevent fan motor
“lock up” from lack of use due to pitting or corrosion over
time.
Page 28 of 37
28
SECONDARY AIR INJECTION
Secondary air injections required to pre-heat the catalytic converters for OBD II compliance.
The system consists of the same components as previous systems with V8 specific loca-
tions.
The DME ME7.2 control unit controls the vacuum vent valve and the secondary air injec-
tion pump relay separately but simultaneously.
The secondary air pump operates at a start temperature of between 10°C and 40°C. It con-
tinues to operate for a max. of 2 minutes at idle speed.
ME 7.2 contributes an additional correction factor for secondary air “on” time with the addi-
tional input from the integral ambient barometric pressure sensor.
This sensor provides a base value to calculate the air mass being
injected into the exhaust system. This helps to “fine tune” the sec-
ondary air injection “on” time, optimizing the necessary air flow
into the exhaust system which reduces the time to catalytic con-
verter light-off.
VACUUM
VACUUM
VENT VALVENONPUMP/MOTOR
AIR PUMP SUPPLY HOSE
AIR DELIVERY TUBE WITH O RING
CONNECTIONS TO CYLINDER HEADS
VACUUM
CONTROL TO
NON RETURN
VA LV E
Page 29 of 37
29
AUXILIARY FAN CONTROL
The Auxiliary Fan motor incorporates an out-
put final stage that activates the fan motor at
variable speeds.
The auxiliary fan is controlled by ME 7.2. The
motor output stage receives power and
ground and activates the motor based on a
PWM signal (10 - 100 Hz) received from the
ME 7.2.
Similar to the aux fan in the E46 with MS 42.0
control, the fan is activated based on the fol-
lowing factors:
• Radiator outlet temperature sensor input exceeds a preset temperature.
• IHKA signalling via the K and CAN bus based on calculated refrigerant pressures.
• Vehicle speed
• Battery voltage level
When the over temperature light in the instrument cluster is on (120
OC) the fan is run in the
overrun function. This signal is provided to the DME via the CAN bus. When this occurs
the fan is run at a frequency of 10 Hz.
FAN MOTOR MODULE
POWER, GROUND & SIGNAL WIRES
