check engine BMW X5 2001 E53 M54 Engine Workshop Manual

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M54engMS43/ST036/6/2000
MS 43 NEW FUNCTIONS
ELECTRONIC THROTTLE SYSTEM - EML
The M54 engine with MS 43 engine control uses an electronic throttle control system
adopted from the ME 7.2 system on the M62 engine. The system incorporates an electric
throttle valve (EDK) and pedal position sensor (PWG) for engine power control.
The MS 43 control module monitors the PWG input and activates the EDK motor based on
the programmed maps for throttle control. The MS 43 module self checks the activation of
the EDK via feedback potentiometers motor on the EDK motor.
Additional functions of the EML system include:
• Cruise control function
• DSC throttle interventions
• Maximum engine and road speed control
ART-SCANDIAGRAM

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M54engMS43/ST036/6/2000
MS 43 NEW FUNCTIONS
EDK THROTTLE POSITION FEEDBACK SIGNALS
EDK FEEDBACK SIGNAL MONITORING & EDK FAILSAFE OPERATION:
• The EDK provides two separate signals from two integral potentiometers (Pot 1 and Pot
2) representing the exact position of the throttle plate.
• EDK Pot 1 provides the primary throttle plate position feedback. As a redundant safe-
ty feature, Pot 2 is continuously cross checked with Pot 1 for signal plausibility.
• If plausibility errors are detected between Pot 1 and Pot 2, MS 43.0 will calculate the
inducted engine air mass (from HFM signal) and only utilize the potentiometer signal that
closely matches the detected intake air mass.
- The MS 43.0 uses the air mass signalling as a “virtual potentiometer” (pot 3) for a
comparative source to provide failsafe operation.
- If MS 43.0 cannot calculate a plausible conclusion from the monitored pots (1 or 2
and virtual 3) the EDK motor is switched off and fuel injection cut out is activated
(no failsafe operation possible).
• The EDK is continuously monitored during all phases of engine operation. It is also
briefly activated when KL 15 is initially switched on as a “pre-flight check” to verify it’s
mechanical integrity (no binding, appropriate return spring tension, etc). This is accom-
plished by monitoring both the motor control amperage and the reaction speed of the
EDK feedback potentiometers. If faults are detected the EDK motor is switched off and
fuel injection cut off is activated (no failsafe operation possible). The engine does how-
ever continue to run extremely rough at idle speed.
• When a replacement EDK is installed, the MS 43.0 adapts to the new component
(required amperage draw for motor control, feedback pot tolerance differences, etc).
This occurs immediately after the next cycle of KL 15 for approximately 30 seconds.
During this period of adaptation, the maximum opening of the throttle plate is 25%.
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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

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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.