Mechanical Changes
In addition to the increased displacement of the M54B30 engine, several mechanical changes were incorporated into the engine for reduced emissions and increased fuel economy.
These changes include
Scheme 424
Scheme 425
- NEW PISTONS - The piston has a shorter skirt compared to the M52 TU and continues with the graphite coating for friction and emission reducing measures. The piston rings have been modified to reduce friction.
- CRANKSHAFT - The crankshaft for the 3 liter M54 is adopted from the S52B32 - M3 engine. The crankshaft for the 2.5 liter is carried over from M52.
- CAMSHAFT - The camshaft for the 3 liter M54 is modified with more lift (9.7 mm) and new valve springs to accommodate the increased lift. The camshaft of the 2.5 liter M54 is carried over from the M52 engine.
- INTAKE MANIFOLD - The intake manifold is modified with shorter ram tubes (20mm shorter on 3 liter/10mm shorter on 2.5 liter). The diameter of the tubes is increased slightly.
- INJECTION VALVES Exploded View Of - The diameter of the injection pintle has increased slightly for the increased displacement of the 3 liter engine. The injector for the 2.5 liter engine carries over from M52. (Scheme 424): Identifying Injection Valve (1 Of 2) (Scheme 425): Locating Injection Valve (2 Of 2)
Non Return Fuel Rail System
The M54 engine with MS 43.0 control uses the non return fuel rail system introduced on the M62 TU engine. The system meets running loss compliance without the use of the 3/2- way solenoid valve currently used on the M52 TU engine.
Identifying Non Return Fuel Rail System. Scheme 426
The regulated fuel supply is controlled by the fuel pressure regulator integrated in the fuel filter. The fuel return line is also located on the filter.
Non Return Fuel Rail System Diagram. Scheme 427
The M54 engine uses an Electronic Controlled Throttle Valve (EDK) for intake air control. The idle control valve and turbulence function of the intake manifold carries over from the M52 TU engine.
Identifying Electronic Controlled Throttle Valve (EDK). Scheme 428
Identifying M54B30 Engine Torque/Power Graph. Scheme 429
Identifying M54B25 Engine Torque/Power Graph. Scheme 430
SIEMENS ENGINE MANAGEMENT SYSTEM
Models: E53 X5, E46, E39, E36 - Z3
3.0 and 2.5 Liter
SOP: 3 liter - 4/00, 2.5 liter 9/00
This new generation Siemens system is designated as MS 43.0.
Siemens MS 43.0 is a newly developed engine management system to meet the needs of Ultra Low Emission Vehicle (ULEV) compliancy and continuing with present systems is also OBD II compliant. This system also includes control of the Motor-driven Throttle Valve (EDK).
The ECM uses a pc-board dual-processor control unit in the SKE housing configuration.
The MS 43.0 ECM is flash programmable as seen with previous systems.
ECM hardware includes
Modular plug connectors featuring 5 connectors in the SKE housing with 134 pins.
- Connector 1 = Supply voltages and grounds
- Connector 2 = Peripheral signals (oxygen sensors, CAN, etc.)
- Connector 3 = Engine signals
- Connector 4 = Vehicle signals
- Connector 5 = Ignition signals
Identifying Modular Plug Connectors. Scheme 431
Special features
- Flash EPROM which is adaptable to several M52 LEV engines and has the capability to be programmed up to 13 times
- Once a control unit is installed and coded to a vehicle it cannot be swapped with another vehicle for diagnosing or replacement (because of EWS 3.3).
Identifying System Overview I-P-O Diagram. Scheme 432
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.
Identifying Electronic Throttle System - EML Diagram. Scheme 433
Additional functions of the EML system include
- Cruise control function
- DSC throttle interventions
- Maximum engine and road speed control
Accelerator Pedal Sensor
The accelerator pedal sensor is similar to the PWG used on the ME 7.2 system. It is integrated into the accelerator pedal housing. Two hall sensors are used to provide the driver's input request for power.
The hall sensors receive power (5 volts) and ground from the MS 43 control module and produce linear voltage signals as the pedal is pressed from LL to VL.
PWG SENSOR 1 = 0.5 to 4.5 V
PWG SENSOR 2 = 0.5 to 2.0 V
The MS 43 control module uses the signal from sensor 1 as the driver's request and the signal from sensor 2 as plausibility checking.
Identifying Accelerator Pedal Sensor Diagram. Scheme 434
Scheme 435
- As a redundant safety feature the PWG provides two separate signals from two integral angle hall sensors (HS #1 and HS #2) representing the driver's request for throttle activation.
- If the monitored PWG signals are not plausible, MS 43.0 will only use the lower of the two signals as the driver's pedal request input providing failsafe operation. Throttle response will be slower and maximum throttle position will be reduced.
- When in PWG failsafe operation, MS 43.0 sets the EDK throttle plate and injection time to idle (LL) whenever the brake pedal is depressed.
- When the system is in PWG failsafe operation, the instrument cluster matrix display will post "Engine Emergency Program" and PWG specific fault(s) will be stored in memory. (Scheme 435): PWG Signal Monitoring PWG Failsafe Operation Graph
EDK Throttle Position Feedback Signals
The EDK throttle plate is monitored by two integrated potentiometers. The potentiometers provide linear voltage feedback signals to the control module as the throttle plate is opened and closed.
Feedback signal 1 provides a signal from 0.5 V (LL) to 4.5 V (VL).
Feedback signal 2 provides a signal from 4.5 V (LL) to 0.5 V (VL)
Potentiometer signal 1 is the primary feedback signal of throttle plate position and signal 2 is the plausibility cross check through the complete throttle plate movement.
Identifying EDK Throttle Position Feedback Signals Diagram. Scheme 436
Identifying EDK Throttle Position Feedback Signals Graph. Scheme 437
Main Relay Monitor
The MS 43.0 system incorporates a new monitoring feature for terminal 87 (KL 87) of the main relay. The relay is monitored internally for the voltage level at KL 87. Five seconds after the ignition key is switched on, and the voltage at the KL 15 input is greater than 9 volts, the control module checks the voltage at KL 87.
If the voltage difference between the two terminals is greater than 3 volts, a fault will be stored in the ECM.
Identifying Main Relay Monitor Diagram. Scheme 438
Emission Optimized - Ignition Key Off
"Emission Optimized Ignition Key Off" is a programmed feature of the MS 43 control module.
After the ECM detects KL 15 being switched OFF, the ignition stays active for two more individual coil firings. This means that just two cylinders are fired - not two revolutions.
This feature allows residual fuel injected into the cylinders, as the ignition key is switched off, to be burned as the engine runs down.
Emission Optimized Ignition Key Off. Scheme 439
Emission Optimized Ignition Key Off Display. Scheme 440
Function
The DC Motor LDP ensures accurate fuel system leak detection for leaks as small as 0.5mm (.020"). The pump contains an integral DC motor which is activated directly by the engine control module. The ECM monitors the pump motor operating current as the measurement for detecting leaks.
The pump also contains an ECM controlled change over valve that is energized closed during a Leak Diagnosis test. The change over valve is open during all other periods of operation allowing the fuel system to "breath" through the inlet filter (similar to the full down stroke of the current vacuum operated LDP).
Checking Tank Leakage Diagram. Scheme 441
Phase 1 - Reference Measurement
The ECM activates the pump motor. The pump pulls air from the filtered air inlet and passes it through a precise 0.5mm reference orifice in the pump assembly.
The ECM simultaneously monitors the pump motor current flow. The motor current raises quickly and levels off (stabilizes) due to the orifice restriction. The ECM stores the stabilized amperage value in memory. The stored amperage value is the electrical equivalent of a 0.5 mm (0.020") leak.
Identifying Leak Diagnosis Test Diagram. Scheme 442
Phase 2 - Leak Detection
The ECM energizes the Change Over Valve allowing the pressurized air to enter the fuel system through the Charcoal Canister, The ECM monitors the current flow and compares it with the stored reference measurement over a duration of time.
Identifying Leak Detection Diagram. Scheme 443
Once the test is concluded, the ECM stops the pump motor and immediately de-energizes the change over valve. This allows the stored pressure to vent thorough the charcoal canister trapping hydrocarbon vapor and venting air to atmosphere through the filter.
Bosch Oxygen Sensors
The MS43.0 system uses Bosch LSH 25 oxygen sensors that function basically the same as previously used (in Bosch systems). The voltage range is between 0-800 mV.
Identifying Pre 02 Sensor. Scheme 444
PRE 02 SENSOR
Identifying Post 02 Sensor. Scheme 445
POST 02 SENSOR
The location remains the same with the pre-cat sensors are mounted on top of the exhaust manifolds. The catalysts are now integral with the exhaust manifolds (further detailed in the M52 TU engine section).
Identifying Post Catalyst Sensors. Scheme 446
Oxygen Sensor Signal Influence On Injector "Open" Time
The ECM monitors the
- Amplitude of the signal (highest voltage or range sensor is producing)
- Switching time of the signal (how fast from lean to rich)
- Frequency of complete cycles (how many within a period of time)
These characteristics provide info to the ECM that reflect the overall condition of the sensor.
Post Catalytic Converter Sensor Signal
The post catalyst O2 sensors monitor the efficiency of the catalyst as a requirement of OBD II. This signal also provides feedback of the pre-catalyst sensors efficiency and can cause the ECM to "trim" the ms injection time to correct for slight deviations.
- If the catalyst is operating efficiently, most of the remaining oxygen in the exhaust gas is burned (lack of O2 - "constant lean signal"). The sensor signal fluctuates slightly in the higher end of the voltage scale.
- If the post sensor shows excessive fluctuations (which echo the scope pattern of the pre sensor), this indicates that the catalytic converter is not functioning correctly and cannot consume the O2 (fault set).
- If the post sensor fluctuations move out of the normal voltage "window", this indicates that the pre sensor is not performing properly due to slight deterioration. These systems can also "trim" the ms injection time to compensate for this.
The constantly changing oxygen sensor input to the ECM is needed to correct the ms injection time to ensure that the ideal air/fuel ratio is maintained.
Camshaft Sensor Intake And Exhaust Camshafts
The "static" Hall sensors are used so that the camshaft positions are recognized once ignition 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
Locating Camshaft Sensor Intake And Exhaust Camshafts. Scheme 447
Crankshaft Sensor
The crankshaft sensor is a dynamic Hall-effect sensor (mounted through the engine block), the signal is sent the moment the crankshaft begins to rotate.
The pulse wheel is mounted directly to the crankshaft as seen on previous models.
Crankshaft Sensor Diagram. Scheme 448
SMOOTH RUNNING ENGINE NOTE SQUARE WAVE ENGINE MISFIRE DETECTED
Misfire Detection
As part of the CARB/OBD regulations the engine control module must determine if misfire is occurring and also identify the specific cylinder(s) and the severity of the misfire event, and whether it is emissions relevant or catalyst damaging. In order to accomplish these tasks the control module monitors the crankshaft for acceleration losses during firing segments of each cylinder based on firing order.
Misfire Detection Example: M54 (6 Cyl.) with Siemens System The misfire/engine roughness calculation is derived from the differences in the period duration (T) of individual increment gear segments. Each segment period consist of an angular range of 120° crank angle that starts 78° before Top Dead Center (TDC).
If the expected period duration is greater than the permissible value a misfire fault for the particular cylinder is stored in the fault memory of the ECM. Depending on the level of misfire rate measured the control unit will illuminate the "Service Engine Soon" light, may cutoff fuel to the particular cylinder and may switch lambda operation to open-loop. All misfire faults are weighted to determine if the misfire is emissions relevant or catalyst damaging.
Emissions Relevant
During an interval of 1000 crankshaft revolutions the misfire events of all cylinders are added and if the sum is greater than a predetermined value a fault will be set identifying the particular cylinder(s). The "Service Engine Soon" light will be illuminated during and after the second cycle if the fault is again present.
Catalyst Damaging
During an interval of 200 crankshaft revolutions the misfire events of all cylinders are added and if the sum is greater than a predetermined value a fault will be set identifying the particular cylinders(s). The "Service Engine Soon" lamp
- On vehicles with a Siemens Control Module (M54 engines) - the lamp will immediately go to a steady illumination since fuel to the injector(s) is removed. Fuel cut-off to the cylinder will resume after several ( << 7) periods of decel if crankshaft sensor adaptation is successfully completed or the engine is shut-off and restarted.
In each case the number of misfire events permitted is dependent on engine speed, load and temperature map.
The process of misfire detection continues well after the diagnostic drive cycle requirements have been completed. Misfire detection is an on-going monitoring process that is only discontinued under certain conditions.
Misfire Detection Is Only Disabled Under The Following Conditions
| REQUIREMENTS | STATUS/CONDITION |
|---|---|
| Engine Speed | > 512 RPM |
| Engine Load | Varying/Unstable |
| Throttle Angle | Varying/Unstable |
| Timing | Timing retard request active (i.e. knock control - ASC, AGS) |
| Engine Start-up | Up to 5 seconds after start-up |
| A/C | Up to 0.5 seconds after A/C activation |
| Decel fuel cut-off | Active |
| Rough road recognition | Active |
| ASC Control | Active |
MISFIRE DETECTION
OBD II - Misfire Faults Table (1 Of 2). Scheme 449
OBD II - Misfire Faults Table (2 Of 2). Scheme 450
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.
Identifying Mass Air Flow Sensor HFM (1 Of 2). Scheme 451
Identifying Mass Air Flow Sensor HFM (2 Of 2). Scheme 452
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 postcombustion 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 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.
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 temperatures.
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) maintaining 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.
Identifying Vanos Camshaft System Diagram. Scheme 453
EXHAUST: Advanced piston moved in
INTAKE: Retard piston moved out
Identifying Deactivated Diagram. Scheme 454
DEACTIVATED
EXHAUST: Advanced piston moved out
INTAKE: Retard piston moved in
Identifying Activated Diagram. Scheme 455
ACTIVATED
Identifying Activated Frequency Chart. Scheme 456
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 provides EGR without the external hardware as seen on previous systems.
Identifying Intake And Exhausrt Flow. Scheme 457
Electric Fan
The electric cooling fan is now controlled by the ECM. The ECM uses a remote power output 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 calculation (sensing ratio) of
Scheme 458
- 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) (Scheme 458): Identifying Electric Fan Diagram
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).
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 cylinder head, with a passageway machined through the head. This eliminates the external Air Injection manifold distribution pipes to the exhaust manifolds.
Identifying Secondary Air Injection. Scheme 459
Secondary Air Injection Monitoring
In order to reduce HC and CO emissions while the engine is warming up, BMW implemented 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 injecting 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
| REQUIREMENTS | STATUS/CONDITION IMS 43.0 | STATUS/CONDITION M73 |
|---|---|---|
| Oxygen sensor | Open Loop | Open Loop |
| Oxygen sensor heating | Active | Active |
| Engine coolant temperature | 10 to 40°C* | 10 to 40°C* 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" |
SECONDARY AIR INJECTION MONITORING
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.
The Secondary Air Injection System is monitored via the use of the pre-catalyst oxygen sensor(s). Once the air pump is active and is air injected into the system the signal at the oxygen sensor will reflect a lean condition. If the oxygen sensor signal does not change within 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 illuminated.
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.
Limitation
For engine/vehicle speed limitation, the ECM will deactivate injection for individual cylinders, allowing a smoother limitation transition. This prevents over-rev when the engine reaches maximum RPM (under acceleration), and limits top vehicle speed (approx. 128 mph).
ECM Deactivating Injection For Individual Cylinders. Scheme 460
RZV Ignition System
The Siemens MS43.0 system uses a multiple spark ignition function. The purpose of multiple ignition is
- Provide clean burning during engine start up and while idling (reducing emissions).
- This function helps to keep the spark plugs clean for longer service life (new BMW longlife plugs).
Identifying RZV Ignition System Diagram. Scheme 461
Multiple ignition is active up to an engine speed of approximately 1350 RPM (varied with engine temperature) and up to 20 degrees after TDC.
Multiple ignition is dependent on battery voltage. When the voltage is low, the primary current is also lower and a longer period of time is required to build up the magnetic field in the coil(s).
- Low battery voltage = less multiple ignitions
- High battery voltage = more multiple ignitions
The 240 ohm shunt resistor is still used on the MS43.0 system for detecting secondary ignition faults and diagnostic purposes.
Resonance/Turbulence Intake System
On the M54, the intake manifold is split into 2 groups of 3 (runners) which increases low end torque. The intake manifold also has separate (internal) turbulence bores which channels air from the idle speed actuator directly to one intake valve of each cylinder (matching bore of 5.5mm in the cylinder head).
Routing the intake air to only one intake valve causes the intake to swirl in the cylinder.
Together with the high flow rate of the intake air due to the small intake cross sections, this results in a reduction in fluctuations and more stable combustion.
Identifying Resonance/Turbulence Intake System Diagram. Scheme 462
Resonance System
The resonance system provides increased engine torque at low RPM, as well as additional power at high RPM. Both of these features are obtained by using a resonance flap (in the intake manifold) controlled by the ECM.
During the low to mid range rpm, the resonance flap is closed. This produces a long/single intake tube for velocity, which increases engine torque.
During mid range to high rpm, the resonance flap is open. This allows the intake air to pull through both resonance tubes, providing the air volume necessary for additional power at the upper RPM range.
When the flap is closed, this creates another "dynamic" effect. For example, as the intake air is flowing into cylinder #1, the intake valves will close. This creates a "roadblock" for the in rushing air. The air flow will stop and expand back (resonance wave back pulse) with the in rushing air to cylinder #5. The resonance "wave", along with the intake velocity, enhances cylinder filling.
The ECM controls a solenoid valve for resonance flap activation. At speeds below 3750 RPM, the solenoid valve is energized and vacuum supplied from an accumulator closes the resonance flap. This channels the intake air through one resonance tube, but increases the intake velocity.
Identifying Resonance Flap. Scheme 463
#1 Cylinder Intake Valve open
Low to Mid Range RPM
(< 3750 RPM)
Identifying Cylinder Intake Valve Open. Scheme 464
#1 Cylinder Intake Valve closes
#5 Intake Valve Opens
=> Intake Air Bounce Effect
Low to Mid Range RPM
(<3750 RPM)
Identifying Resonance Operation System Diagram (1 Of 3). Scheme 465
#1 Cylinder Intake Valve open -Intake air drawn from both resonance tubes.
Mid to High Range RPM
(>3750 RPM)
Identifying Resonance Operation System Diagram (2 Of 3). Scheme 466
#5 Cylinder Intake Valve open -Intake air drawn from both resonance tubes.
Mid to High Range RPM
(>3750 RPM)
Identifying Resonance Operation System Diagram (3 Of 3). Scheme 467
Idle Speed Control
The ECM determines idle speed by controlling an idle speed actuator (dual winding rotary actuator) ZWD 5.
The basic functions of the idle speed control are
Scheme 468
- Control the initial air quantity (at air temperatures <0 C, the EDK is simultaneously opened)
- Variable preset idle based on load and inputs
- Monitor RPM feedback for each preset position
- Lower RPM range intake air flow (even while driving)
- Vacuum limitation
- Smooth out the transition from acceleration to deceleration (Scheme 468): Identifying Idle Speed Control System Diagram
Under certain engine operating parameters, the EDK throttle control and the idle speed actuator (ZWD) are operated simultaneously.This includes All idling conditions and the transition from off idle to load.
As the request for load increases, the idle valve will remain open and the EDK will supply any additional air volume required to meet the demand.
Emergency Operation of Idle Speed Actuator
If a fault is detected with the idle speed actuator, the ECM will initiate failsafe measures depending on the effect of the fault (increased air flow or decreased air flow).
If there is a fault in the idle speed actuator/circuit, the EDK will compensate to maintain idle speed. The EML lamp will be illuminated to inform the driver of a fault.
If the fault causes increased air flow (actuator failed open), VANOS and Knock Control are deactivated which noticeably reduces engine performance.
Cruise control
Cruise control is integrated into the ECM because of the EDK operation.
Cruise control functions are activated directly by the multifunction steering wheel to the ECM. The individual buttons are digitally encoded in the MFL switch and is input to the ECM over a serial data wire.
Identifying Cruise Control Diagram. Scheme 469
The ECM controls vehicle speed by activation of the Electronic Throttle Valve (EDK) The clutch switch disengages cruise control to prevent over-rev during gear changes.
The brake light switch and the brake light test switch are input to the ECM to disengage cruise control as well as fault recognition during engine operation of the EDK.
Road speed is input to the ECM for cruise control as well as DSC regulation. The vehicle speed signal for normal engine operation is supplied from the DSC module (right rear wheel speed sensor). The road speed signal for cruise control is supplied from the DSC module.
This is an average taken from both front wheel speed sensors, supplied via the CAN bus.
Purge Valve
The purge valve (TEV) is activated at 10 Hz by the ECM to cycle open, and is sprung closed. The valve is identical to the purge valve used on the Siemens MS 42 system.
