Page 13 of 37
13
ENGINE COOLING SYSTEM
The cooling system concepts introduced in
the 1999 Model year including the automatic
transmission heat exchanger and the the
water cooled alternator have been retained
for the X5.
The component locations have however
been changed:
• Thermostat for heat exchanger mounted
directly on radiator
• Transmission heat exchanger - right side
of radiator.
Page 14 of 37
14
IHKA SYSTEM AUXILIARY PUMP
The auxiliary water pump for the IHKA is mounted on the left side of the radiator. The func-
tion of the pump remains the same as follows:
• provide adequate coolant flow for IHKA opera-
tion.
• provide coolant circulation for the REST function
of IHKA.
Page 22 of 37
22
RADIATOR OUTLET TEMP SENSOR
First seen on the MS 42.0 control system, the ME
7.2 uses an additional water temperature sensor
located on the radiator outlet.
ME 7.2 requires this signal to monitor the water
temperature leaving the radiator for precise acti-
vation of the IHKA auxiliary fan.
DSC III - ROAD SPEED SIGNAL
ME 7.2 receives the road speed signal directly
from the DSC III control module for maximum
vehicle speed management. The DSC control
module provides a processed output of the right
rear wheel speed sensor as a digital square wave
signal. The frequency of the signal is proportion-
al to the speed of the vehicle (48 pulses per one
revolution of the wheel).
The cruise control function (FGR) of the ME 7.2 also monitors vehicle speed from the redun-
dant vehicle speed CAN bus signal. The CAN bus speed signal is provided by the DSC III
control module and based on the combined average of both front wheel speed signals.
Additionally, ME 7.2 monitors all four wheel speed signals via CAN bus signalling to detect
abrupt fluctuations in vehicle speed signals for the purpose of detecting rough road sur-
faces. This is continuously monitored as part of the OBD II emission requirements provid-
ing a correction factor for misfire detection plausibility. Earlier systems only monitored the
right rear speed signal input from DSC.
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
