battery BMW 735i 2001 E38 M62TU Engine Workshop Manual

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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

LEAK DIAGNOSIS TEST PRECONDITIONS
The DME only initiates a leak diagnosis test every second time the criteria are met. The cri-
teria is as follows:
• Engine OFF with ignition switched OFF.
• Engine Control Module still in active state or what is known as “follow up mode” (Main
Relay energized, control module and DME components online for extended period after
key off).
• Prior to Engine/Ignition switch OFF condition, vehicle must have been driven for a min-
imum of 20 minutes.
• Prior to minimum 20 minute drive, the vehicle must have been OFF for a minimum of 5
hours.
• Fuel Tank Capacity must be between 15 and 85%(safe approximation between 1/4 -
3/4 of a tank).
• Ambient Air Temperature between -7
OC & 35OC(20OF & 95OF )
• Altitude < 2500m(8,202 feet).
• Battery Voltage between 11.5 and 14.5 Volts
When these criteria are satisfied every second time, the ECM will start the Fuel System Leak
Diagnosis Test. The test will typically be carried out once a day i.e. once after driving to
work in the morning, when driving home in the evening, the criteria are once again met but
the test is not initiated. The following morning, the test will run again.
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