BMW 3 (E46). Manual — part 31

(ECT) in cylinder head supplies
coolant temperature information to
the ECM.

ECM outputs:

Fuel injector opening duration.

Intake and exhaust valve timing via
the VANOS system.

The radiator cooling fan and the
heated coolant thermostat.

Motor-driven throttle valve: MDK in
MS 42.0 or EDK in MS 43.0.

Idle speed control valve (MS 42.0)

Resonance valve in the intake
manifold.

ECM outputs (cont.):

MS 42.0: Fuel pressure via 3/2 way
valve monitors running losses
(evaporative losses during engine
operation).

Secondary air injection (if
applicable) to reduce HC and CO.

Multiple spark ignition system.

Maximum vehicle speed and cruise
control.

Brake booster vacuum pump.

Fuel purge valve and fuel tank
leakage diagnosis pump (LDP or
DM-TL).

Fuel metering: The ECM meters
pressurized fuel by changing the
opening time (pulse width) of the fuel
injectors. The exact amount of fuel
injected is determined by the amount of
time the injectors are open. To ensure
that injector pulse width is the only factor
that determines fuel metering, fuel pump
pressure is maintained by a pressure
regulator. The injectors are mounted to a
common fuel rail.

The ECM monitors engine operating
conditions to determine injector opening
duration. Each injector can be
individually controlled for cylinder
selective fuel trim. The fuel-injectors
inject fuel at an angle in a dual cone
spray pattern.

Air intake: Air entering the engine passes
through a pleated paper air filter in the
air cleaner. Intake air mass is then
measured by a mass air flow (MAF)
sensor. A reference current is used to
heat a thin film in the sensor when the
engine is running. The current needed to
hold the temperature of the film constant
is the basis of the electronically
converted voltage measurement
corresponding to the mass of the intake
air.

Idle speed control: Idle speed is
electronically controlled via the idle
speed control valve by bypassing
varying amounts of air around the closed
throttle valve. Idle speed is not
adjustable. The ECM determines idle
speed by controlling a dual-winding
rotary idle control valve. The basic
functions and parameters of idle speed
control are as follows:

Control of cold air intake volume.
For example, at air temperatures
below 0°C (32°F), electronic throttle
control (MDK/EDK) is also opened
during idle.

Smooth idle speeds regardless of
load and inputs

Lower rpm range

Smooth transition from acceleration
to deceleration

Idle speed stabilization is active during
the following conditions:

Engine warm up

A/C activation

Drive gear selected (auto.
transmission)

During passenger compartment
heating

During different cooling fan speeds

If the ECM detects a fault in the idle
control valve, it will increase or decrease
air flow, depending on the nature of the
fault:

If the fault causes decreased air
flow (idle control valve closed), the
electronic throttle control (MDK or
EDK) will compensate to maintain
idle. The EML lamp will illuminate to
inform the driver of a fault.

If the fault causes increased air flow
(actuator failed open), VANOS and
knock control are deactivated. This
reduces engine performance
noticeably.

Throttle control: The throttle valve plate
is electronically operated for precise
throttle operation, OBD II compliant for
fault monitoring, and ASC/DSC and
cruise control. This integrated electronic
throttle reduces additional control
modules, wiring and sensors. Adjusting
electronic throttles is not permitted and
the throttle assembly must be replaced
as a unit if found to be faulty.

The throttle assembly for the MS 42.0
system is referred to as the MDK (Motor
Driven Throttle Valve). The MDK is
identified as follows:

A throttle cable is used to actuate
the accelerator pedal position
potentiometers and also serves as a
backup to open the throttle plate
(full control) when the MDK system
is in the failsafe mode.

The throttle assembly for the MS 43.0
system is referred to as the EDK
(Electronic Throttle Valve). The EDK is
identified as follows:

The accelerator position
potentiometers (PWG) are located
in the accelerator pedal assembly.

The EDK is fully electronic. The
accelerator pedal is not
mechanically linked to the EDK.