2002 BMW X5 Air

26
M54engMS43/ST036/6/2000
CAMSHAFT SENSOR
-INTAKE AND EXHAUST CAMSHAFTS
The "static" Hall sensors are used so that the camshaft positions are recognized once igni-
tion is “on” - even before the engine is started.
The function of the intake cam sensor:
• Cylinder bank detection for preliminary injection
• Synchronization
• Engine speed sensor (if crankshaft speed sensor fails)
• Position control of the intake cam (VANOS)
The exhaust cam sensor is used for position control of the exhaust cam (VANOS)
If these sensors fail there are no substitute values, the system will operate in the failsafe
mode with no VANOS adjustment. The engine will still operate, but torque reduction will be
noticeable.
NOTE: Use caution on repairs as not to bend the impulse wheels
KL 15 KL 15
MS42.0
SOLENOID
OIL TEMP.
SENSOR TWO POSITION PISTON HOUSING
WITH INTERNAL/EXTERNAL
HELICAL GEAR CUP TWO POSITION PISTON
HOUSING WITH
INTERNAL/EXTERNAL
HELICAL GEAR CUP
ENGINE
OIL SUPPLY VENT VENT
SOLENOID
SENSOR SENSOR
MS42
ECM
EXHAUST
INTAKE
MS42.0
ECM
MS 43.0
MS 43.0
MS 43.0

31
M54engMS43/ST036/6/20000
MASS AIR FLOW SENSOR HFM
The Siemens mass air flow sensor is functionally the same as in the past. The designation
2 Type B simply indicates that it is smaller in design. The mass air meter has a diameter of
85 mm.
________________________________________________________________
________________________________________________________________
________________________________________________________________

32
M54engMS43/ST036/6/2000
MS 43 CARRY OVER FUNCTIONS
OUTPUT FUNCTIONS -VANOS CONTROL
With the double VANOS system, the valve timing is changed on both the intake and the
exhaust camshafts.
Double VANOS provides the following benefits:
• Torque increase in the low to mid (1500 - 2000 RPM) range without power loss in the
upper RPM range.
• Less incomplete combustion when idling due to less camshaft overlap (also improves
idle speed characteristics).
• Internal exhaust gas recirculation (EGR) in the part load range (reduces NOx and post-
combustion of residual gasses in the exhaust)
• Rapid catalyst warm up and lower “raw” emissions after cold start.
• Reduction in fuel consumption
Double VANOS consists of the following parts:
• Intake and exhaust camshafts with helical gear insert
• Sprockets with adjustable gears
• VANOS actuators for each camshaft
• 2 three-way solenoid switching valves
• 2 impulse wheels for detecting camshaft position
• 2 camshaft position sensors (Hall effect)
The “initial” timing is set by gear positioning (refer to the Repair Instructions for details) and
the chain tensioner. As with the previous VANOS, the hydraulically controlled actuators
move the helical geared cups to regulate camshaft timing. The angled teeth of the helical
gears cause the pushing
movement of the helical cup to be converted into a rotational
movement. This rotational movement is added to the turning of the camshafts and cause
the camshafts to “advance” or “retard”. The adjustment rate is dependent oil temperature,
oil pressure, and engine RPM.

33
M54engMS43/ST036/6/20000
NOTE: With extremely hot oil temperatures Vanos is deactivated (Power loss). If the oil is
too thick (wrong viscosity) a fault could be set.
When the engine is started, the camshafts are in the “failsafe” position (deactivated). The
intake camshaft is in the RETARDED position - held by oil pressure from the sprung open
solenoid. The exhaust camshaft is in the ADVANCED position - held by a preload spring in
the actuator and oil pressure from the sprung open solenoid.
After 50 RPM (2-5 seconds) from engine start, the ECM is monitoring the exact camshaft
position.
The ECM positions the camshafts based on engine RPM and the throttle position signal.
From that point the camshaft timing will be varied based on intake air and coolant temper-
atures.
The double VANOS system is “fully variable”. When the ECM detects the camshafts are in
the optimum positions, the solenoids are modulated (approximately 100-220 Hz) maintain-
ing oil pressure on both sides of the actuators to hold the camshaft timing.
CAUTION:
The VANOS MUST
be removed and installed exactly as described in the Repair
Instructions!
NOTE: If the VANOS camshaft system goes to the failsafe mode (deactivated) there will be
a noticeable loss of power. This will be like driving with retarded ignition or starting from a
stop in third gear.
KL 15 KL 15
MS42.0
SOLENOID
OIL TEMP.
SENSOR TWO POSITION PISTON HOUSING
WITH INTERNAL/EXTERNAL
HELICAL GEAR CUP TWO POSITION PISTON
HOUSING WITH
INTERNAL/EXTERNAL
HELICAL GEAR CUP
ENGINE
OIL SUPPLY VENT VENT
SOLENOID
SENSOR SENSOR
MS42
ECMEXHAUST
INTAKE
MS42.0
ECM
MS 43.0
MS 43.0
MS 43.0

35
M54engMS43/ST036/6/20000
The dual VANOS in conjunction with the variable intake manifold provides an additional
emission control feature.
Because of the improved combustion, the camshaft timing is adjusted for more overlap.
The increased overlap supports internal exhaust gas recirculation (EGR) which reduces
tailpipe emissions and lowers fuel consumption.
During the part load engine range, the intake camshaft overlap opens the intake valve. This
allows limited exhaust gas reflow the intake manifold.
The “internal” EGR reduces the cylinder temperature thus lowering NOx. This feature pro-
vides EGR without the external hardware as seen on previous systems.
INLET
TURBULENCE
IDLE AIR
CONTROL VALVEMDK
INT. EGR
CATALYST
CLOSE TO
ENGINESECONDARY
AIR
INJECTION
(AIR FILTER)OUTLET-VANOS
(228/80-105)INLET-VANOS
(228/80-120)

36
M54engMS43/ST036/6/2000
ELECTRIC FAN
The electric cooling fan is now controlled by the ECM. The ECM uses a remote power out-
put final stage (mounted on the fan housing)
The power output stage receives power from a 50 amp fuse (located in glove box above
the fuse bracket). The electric fan is controlled by a pulse width modulated signal from the
ECM.
The fan is activated based on the ECM calcula-
tion (sensing ratio) of:
• Coolant outlet temperature
• Calculated (by the ECM) catalyst temperature
• Vehicle speed
• Battery voltage
• Air Conditioning pressure (calculated by IHKA
and sent via the K-Bus to the ECM)
NOTE: If the ECM indicates a fault check the fan for freedom of movement
After the initial test has been performed, the fan is brought up to the specified operating
speed. At 10% (sensing ratio) the fan runs at 1/3 speed. At a sensing ratio of between 90-
95% the fan is running at maximum speed. Below 10% or above 95% the fan is stationary.
The sensing ratio is suppressed by a hysteresis function, this prevents speed fluctuation.
When the A/C is switched on, the electric fan is not immediately activated.
After the engine is switched off, the fan may continue to operate at varying speeds (based
on the ECM calculated catalyst temperature). This will cool the radiator down from a heat
surge (up to 10 minutes).
OUTPUT STAGE
MS42.0
POWER
MS 43.0

37
M54engMS43/ST036/6/20000
SECONDARY AIR INJECTION
This ECM controlled function remains unchanged from
the previous Siemens MS system, however there is a
hardware change.
The Air Injection Inlet Valve mounts directly to the cylin-
der head, with a passageway machined through the
head. This eliminates the external Air Injection manifold
distribution pipes to the exhaust manifolds.
SECONDARY AIR INJECTION MONITORING
In order to reduce HC and CO emissions while the engine is warming up, BMW imple-
mented the use of a Secondary Air Injection System in. Immediately following a cold engine
start (-10 - 40°C) fresh air/oxygen is injected directly into the exhaust manifold. By inject-
ing oxygen into the exhaust manifold:
• The warm up time of the catalyst is reduced
• Oxidation of the hydrocarbons is accelerated
The activation period of the air pump can vary depending on engine type and operating
conditions.
Conditions for Secondary Air Pump Activation:
*NOTE: Below -10°C the air injection pump is activated only as a preventive measure to
blow out any accumulated water vapor that could freeze in the system.
REQUIREMENTS STATUS/CONDITION
M52 & M44STATUS/CONDITION
M73
Oxygen sensor Open Loop Open Loop
Oxygen sensor heating Active Active
Engine coolant temperature -10 to 40ºC* -10 to 40ºC* Stage
Engine bad Predefined Range Predefined Range
Engine speed Predefined Range Predefined Range
Fault Codes No Secondary Air Faults
“currently present”
No Secondary Air Faults
“currently present”
MS 43.0

38
M54engMS43/ST036/6/2000
The Secondary Air Injection System is monitored via the use of the pre-catalyst oxygen sen-
sor(s). Once the air pump is active and is air injected into the system the signal at the oxy-
gen sensor will reflect a lean condition. If the oxygen sensor signal does not change with-
in a predefined time a fault will be set and identify the faulty bank(s). If after completing the
next cold start and a fault is again present the "Service Engine Soon" light will be illuminat-
ed.
Example: Secondary Air Injection Monitoring (M54-Siemens System)
During a cold start condition air is immediately injected into the exhaust manifold and since
the oxygen sensors are in open loop at this time the voltage at the pre catalyst sensor will
reflect a lean condition) and will remain at this level while the air pump is in operation. Once
the pump is deactivated the voltage will change to a rich condition until the system goes
into closed loop operation.
M54 System Operation:
The pump draws air through its own air filter and delivers it to both exhaust manifolds
through a non-return (shutoff valve). The non-return valve is used to:
1. Control air injection into the exhaust manifold - A vacuum controlled valve will open the
passageway for air to be injected once a vacuum is applied.
2. Prevent possible backfires from traveling up the pipes and damaging the air pump when
no vacuum is applied.
The control module activates the vacuum vent valve whenever the air pump is energized.
Once the vacuum vent valve is energized a vacuum is applied to the non-return valve which
allows air to be injected into the exhaust manifold. A vacuum is retained in the lines, by the
use of a check valve, in order to allow the non-return valve to be immediately activated on
cold engine start up. When the vacuum/vent valve is not energized, the vacuum to the
non-return valve is removed and is vented to atmosphere.