3 Series E46 316Ci (N45) COUPE
•
Load
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Engine speed
The pressure created by the secondary air pump opens the secondary air valve in the direction of the exhaust
manifold. When closed, the secondary air valve protects the secondary air pump from deposits due to exhaust
fumes.
When the secondary air pump is activated, the oxygen-sensor voltage is monitored by the DME control unit.
Providing the secondary air system is working correctly, the oxygen-sensor voltage generally falls within the lean
range.
The oxygen-sensor voltage is now registered by the DME control unit at regular intervals (every 20 ms). If an
oxygen-sensor voltage measured falls in the lean range, an internal counter is increased.
Once this counter exceeds a defined threshold value, the system is determined to be fully functional. If this
threshold value is not reached, the DME control unit registers a fault in the secondary air system (fault memory
entry).
Evaluation of road speed signal
The road speed signal is required by the DME control unit in order to perform several functions:
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Cruise control:
Once the maximum road speed has been reached, the fuel preparation and ignition are adjusted. If
required, individual ignition and injection signals are suppressed. A "soft" speed limiting function is thus
carried out.
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Control of A/C compressor:
When the air-conditioning system is switched on, the A/C compressor is switched off during full-load
acceleration,
provided that: the car's road speed is less than 13 km/h.
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Idle speed control:
When the vehicle is at a standstill, the idle speed is controlled around a fixed value (fixed slightly above
engine speed at standstill).
If the car's road speed is 0 km/h, the idle speed is adjusted (depends on A/C compressor ON, selected
drive position for automatic transmission, light ON).
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Poor-road-surface detection:
At low road speeds, the check for smooth engine operation is switched off.
Monitoring of oil level and engine oil pressure
The thermal oil level sensor reports the engine oil level and engine oil temperature back to the DME control unit.
A temperature sensor in the oil-level sensor indicates the engine oil temperature. The oil pressure is indicated by
the oil-pressure switch.
Calculation of oil level:
The DME control unit works out the time required to heat up and cool the engine oil.
The DME control unit activates the warning and indicator lamp in the instrument cluster via the PT-CAN (red: oil
pressure low; yellow: oil level low).
> E60, E81, E87, E90, E91, E92, E93 with electronic oil level check:
The oil dipstick, including the guide tube, is no longer provided on engines N45/N45TU2 and N46/N46TU2. The
engine oil level is measured by a thermal oil level sensor. The measured value is displayed by means of a bar
gauge in the instrument cluster.
On vehicles with Central Information Display, the measured value is displayed on the CID.
The signal from the thermal oil level sensor is evaluated by the DME. Besides the oil level, the thermal oil level
SBT Engine control for N45, N46 E46, E60, E81, E83, E85, E87, E90, E91, E92, E93
BMW AG - TIS
19.01.2013 04:18
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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