Engine Controls - Theory & Operation BMW X5 E53

INTRODUCTION

This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar.

COMPUTERIZED ENGINE CONTROLS

Powertrain Control Module (PCM) receives and processes sensor input and sends output signals to adjust injector pulse widths and ignition timing. Systems can be diagnosed using generic scan tool or, for more complete diagnosis, using BMW Mobile Diagnostic Information Center (MoDiC). (Scheme 1) See BMW MODIC DIAGNOSTIC TESTER. Engine management system, which operates in conjunction with other computer-controlled systems, controls fuel injection and ignition under variable operating conditions. Engine management system controls air/fuel mixture and exhaust emissions by adjusting fuel injection and ignition timing. See ENGINE MANAGEMENT SYSTEM table.

Scheme 1

POWERTRAIN CONTROL MODULE (PCM)

All models use an PCM with 9-pin, 24-pin, 40-pin and 52-pin connectors. (Scheme 2)- (Scheme 5). For PCM location, see PCM CONTROL UNIT LOCATION table. PCM uses intake airflow, intake air temperature, throttle position, coolant temperature, engine speed, vehicle speed, crankshaft position, knock sensors and exhaust gas oxygen content intake signals to determine optimum fuel injection and ignition timing.

PCM CONTROL UNIT LOCATION

Scheme 2

Scheme 3

Scheme 4

Scheme 5

PCM can operate engine in a limp-in mode, allowing vehicle operation despite component failure. PCM also has adaptive capabilities to compensate for component wear and other factors, such as minor vacuum leaks. Once a fault is recognized, it is stored in PCM memory as a Diagnostic Trouble Code (DTC). The system automatically substitutes a fixed replacement value for the incorrect value caused by a defective component or circuit. An air/fuel ratio of 14.7:1 is maintained under most driving conditions. Maximum engine RPM is limited by PCM by eliminating power to fuel injectors.

Note. Components are grouped into 2 categories. The first category covers input devices, which control or produce voltage signals monitored by PCM. See INPUT DEVICES (MOTRONIC) or INPUT DEVICES (SIEMENS) . The second category covers output signals, which are components controlled by PCM. See OUTPUT SIGNALS (MOTRONIC) or OUTPUT SIGNALS (SIEMENS) .

ENGINE MANAGEMENT SYSTEM

BMW MODIC DIAGNOSTIC TESTER

The BMW Mobile Diagnostic Information Center (MoDiC) was developed to meet the diagnostic needs of BMW vehicles for the future. It compliments the Diagnostic Information System (DIS) tester as a diagnostic tool that enables the technician to quickly troubleshoot electronic faults and problems with the vehicles. The advantage of the MoDiC is its mobility. You have the ability to take the tester anywhere in the workshop and to the vehicle. It can also remain connected to the vehicle while it is driven to check for intermittent problems or conditions that only occur while the vehicle is driven. The MoDiC is a personal computer with

1. Interchangeable batteries.
2. UNIX operating system.
3. 3 Gigabyte hard drive for data/program storage.
4. 32 MB working memory.
5. 90 megahertz Pentium processor.
6. Diagnosis Information System (DIS).
7. Technical Information System (TIS).
8. Digital multimeter.
9. Counter.
10. Single channel oscilloscope.

BMW Diagnostic Concept

BMW diagnosis proceeds directly from the faults and their symptoms. Not only does this minimize time and effort but the quality of repair services can be significantly enhanced. Troubleshooting has become an integrated procedure covering all systems at once. The diagnosis program suggests a test schedule and determines the sequence of tests. These features allow faults to be located more easily and with greater precision. Diagnostic procedural steps are

1. Start of diagnosis.
2. Vehicle identification.
3. Brief test (mandatory).
4. Fault symptom selection.
5. DIS test schedule (inspection plan).
6. Processing of test modules (test information).
7. Examining results of diagnosis.

The number and sequence of test schedule items is calculated on the basis of seriousness of the symptom and number of times the symptom has been observed. Test results are continually analyzed, and the inspection plan is revised accordingly. Test results can be assigned one of the following status items

1. Test not performed.
2. Test performed, result okay. If the result of a test module is okay, the test modules subordinate to that module are not included in the test schedule.
3. X = not okay. If the result of a test module is not okay, the test modules subordinate to that module are included in the test schedule.
4. ? = Result not known/test interrupted.
5. > = Test is being carried (currently active). The results of tests already completed influence the order of preference set up for remaining test modules. Use continue arrow to proceed to next test. DIS/MoDiC highlights test which should be carried out next. The results of tests already completed are indicated to the left of the test designations. The test schedule is revised each time test schedule screen is reentered following the completion of a module. If a fault has been rectified or its symptoms have changed, this is indicated in the inspection plan display (sequence of test modules). Fault memory contents are assessed according to various criteria (e.g. frequency, temperature).

Start Of Diagnosis

Call up the diagnosis program and select the appropriate vehicle. The tester mode is now installed according to information stored in the equipment network so vehicle can be identified (E39, E46, etc.).

Vehicle Identification

Vehicle ID is carried out on the basis of control module data (EWS and IKE/Cluster ZCS) For automatic ID, the DIS or MoDiC reads the ZCS code to determine what systems are installed in the vehicle and directly seeks them out. This process is much faster than previous method of polling all systems possible for a specific vehicle series. If the "D" bus is faulted or the tester can not communicate for whatever reason, manual ID is required.

When either manual or automatic vehicle identification has been completed, the VEHICLE SYSTEM screen appears. The brief test must be carried out before diagnosis can take place. Carry out the brief test to interrogate the fault memories of all control systems. The system contacts the control modules directly to check if the control module is installed and capable of communication. The status of the control module is then displayed in the Vehicle ID screen. Another option is to check control modules for individual interrogation by pressing the systems individually from the screen. Correct vehicle identification is the first essential step for both system guided and user guided troubleshooting.

Fault Symptom Selection

Once the brief test has been completed, use the continue arrow (bottom right) to call up the fault symptom selection screen. The fault symptom selection screen displays all fault memories set for troubleshooting purposes. Service technicians can enter fault symptoms observed by themselves or by the vehicle owner. This is done by selecting the appropriate items in a predefined list of symptoms. Several fault symptoms can be selected simultaneously. Use the transfer key to transfer selected fault symptoms into the display The test schedule is generated on the basis of both the symptoms observed by customers or service technician and the contents of the fault memories.

Test Schedule

Test schedule is generated specifically for the problem at hand based on all current fault symptoms including those stored in fault memories of other control modules. Diagnosis tests are prioritized in an order established by the MoDiC/DIS. Test schedule screen displays one or several symptoms, diagnosis tests and corresponding test modules.

The number and sequence of test schedule items is calculated on the basis of seriousness of the symptom and number of times the symptom has been observed. Test results are continually analyzed, and the inspection plan is revised accordingly. Test results can be assigned one of the following status items (listed in on line help)

1. Test not performed, or test performed, result okay. If the result of a test module is okay, the test modules subordinate to that module are not included in the test schedule.
2. X = not OK If the result of a test module is not OK, the test modules subordinate to that module are included in the test schedule.
3. ? = result not known test interrupted?
4. = > = test is being carried (currently active). The results of tests already completed influence the order of preference set up for remaining test modules. Use the continue arrow to proceed to the next test. DIS/MoDiC highlights the test which should be carried out next (dark background). The results of tests already completed are indicated to the left of the test designations. Test schedule is revised each time TEST SCHEDULE screen is reentered following the completion of a module. If a fault has been rectified or its symptoms have changed, this is indicated in INSPECTION PLAN display (sequence of test modules). Fault memory contents are assessed according to various criteria (e.g. frequency, temperature).

Test Information

Press continue arrow to advance to the next test schedule. Test information screen appears automatically. The test information screen automatically displays documents including: wiring schematics, functional descriptions, connector locations, etc. Test dialog box displays test points and nominal values automatically. This screen format is used throughout the diagnostic software for all systems.

Measurement System

Measurement system is an integral part of the test procedure. It displays automatically when needed by the test schedule. Measurement instructions are provided in bottom right dialogue box as voltage measurement MFK 1 (+) ON (circuit name) or MFK 1 (-) ON ground. All measurements relate to circuit name acronyms that are hot spot activated (if needed). Nominal values are displayed with the actual measured display.

If using a DVOM for measuring values in place of DIS/MoDiC MFK leads, enter measured values into system and follow test plan by pressing measurement system value display bar to bring up a key pad. Enter measured value into key pad and press enter button. DIS /MoDiC uses entered values to continue with test plan. Before diagnosis is terminated, a dialogue box reminds user to print diagnosis report. Diagnosis reports must be printed when diagnosis session is active. Once terminated, diagnosis report cannot be accessed for print. Dialogue box offers the following options

1. TERMINATE ends diagnosis without printing the diagnosis report.
2. DIAGNOSIS REPORT prints report before terminating.

Expert Mode Troubleshooting

Expert mode troubleshooting can be activated at any time during system guided troubleshooting. To operate, press operating button in the navigation line to access documents, function and component selection, and test schedule screens. To return to system guided diagnosis, press appropriate button. Any documents assigned to the diagnosis test which is currently active may be viewed. A new diagnosis test can be selected at any time in FUNCTION AND COMPONENT SELECTION. Press TEST SCHEDULE button to call up the test modules assigned to diagnosis tests. A second schedule list, OWN TEST SCHEDULE now displays test modules assigned to selected diagnosis tests.

Control Unit Functions

Troubleshooting information is also available in the form of control module identification, status and component activation. Read and clear fault memory by pressing control unit functions button. Only control modules identified during brief test can perform control unit functions. Service functions such as adaptation value clearing and automatic transmission fluid level checking are also found in this area.

Basic Troubleshooting (BMW Diagnostic System)

Personally verify customer complaint. Verify that complaint is truly a system malfunction. Perform QUICK TEST to determine if vehicle systems have logged fault codes. Call up faulted system or appropriate test schedule to verify correct control module is installed in car. Follow Diagnostic Information System (DIS) on screen instructions and perform all tests as specified. Use DIS and fault symptom diagnostic procedures. Follow appropriate test module procedures for systems that malfunction but fail to set faults in memory.

7-Series V12

Motronic DME 5.2.1 is used for the M73 TU 750iL. This engine management system includes minimum idle speed reduction (530 RPM), long-life spark plugs, input signal from radiator outlet temperature sensor, E-CAT control program function responsibility of DME, CAN bus configuration is completely twisted pair wiring, electrically heated coolant system map thermostat, 2-speed secondary air injection system control, expanded pin assignments to improve comprehensive component monitoring, variable IHKA auxiliary condenser fan speed control, air shrouded fuel injectors with dual cone spray pattern, and main relays are manufactured with an internal control circuit power supply splice off terminal No. 30 (terminal No. 86 is omitted). The air shrouded fuel injectors of the M73 TU incorporate a new dual port injection spray plate in the injector tip that produces a dual cone spray pattern. The dual cone spray pattern improves atomization by separating the spray jets into 2 streams. Injectors have a value of 15 ohms.

Scheme 6

X5 & 7-Series V8

The ME designation identifies the system as "M" (Motronic) and "E" (EML). System features

1. Manufactured by Bosch to BMW specifications.
2. 134-pin SKE (Standard Shell Construction) control module located in "E" box.
3. Diagnostic communication protocol-KWP2000.
4. Uses Breakout Box (90 88 6 121 300).
5. Integral EML throttle control system monitors an interior installed PWG and actuates an electric throttle valve (EDK).
6. Integral cruise control functionality monitors cruise control requests, brake pedal and clutch switches, and carries out throttle control directly via EDK.
7. Carries out DSC-III torque reduction requests.
8. VANOS control.
9. Integrated altitude sensor.
10. Integrated temperature sensor for monitoring "E" box temperature.
11. Control of "E" box fan.
12. One touch engine start control.
13. Oxygen sensor heating.
14. Engine over-rev and max speed limitation.
15. Active Hall sensor for camshaft position monitoring.
16. Single speed secondary air injection system.
17. Electrically heated coolant system thermostat.
18. Long-life spark plugs.
19. IHKA auxiliary fan control.
20. Diagnostic Module - Tank Leak Diagnosis System (DM-TLD)

Integral Electric Throttle System (EML) Functional Description

When the accelerator pedal is moved, the PWG provides a change in the monitored signals. The X5 ME 7.2 compares the input signal to a programmed map and appropriately activates the EDK motor via proportionally high/low switching circuits. The control module self-checks its activation of the EDK motor via the EDK feedback potentiometers. (Scheme 7) Requirements placed on the Electric Throttle System (EML)

1. Regulate the calculated intake air load based on PWG input signals and programmed mapping.
2. Control idle air with regard to road speed as per previous systems.
3. Monitor driver's input request for cruise control operation.
4. Automatically position EDK for accurate cruise control operation.
5. Perform all DSC III throttle control interventions.
6. Monitor and carry out maximum engine and road speed cutout.

Scheme 7

PWG Signal Monitoring & PWG Failsafe Operation

As a redundant safety feature the PWG provides 2 separate signals from 2 integral potentiometers (pot 1 and pot 2) representing the driver request for throttle activation. If the monitored PWG potentiometer signals are not plausible, ME 7.2 will only use the lower of the 2 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, ME 7.2 sets EDK throttle plate and injection time to idle whenever brake pedal is depressed. When the system is in PWG failsafe operation, the instrument cluster matrix display will post ENGINE EMERGENCY PROBLEM and PWG specific fault(s) will be stored in memory.

EDK Feedback Signal Monitoring & EDK Failsafe Operation

The EDK provides 2 separate signals from 2 integral potentiometers (pot 1 and pot 2) representing the exact position of the throttle plate. EDK pot No. 1 provides the primary throttle plate position feedback. As a redundant safety feature, pot No. 2 is continuously cross checked with pot No. 1 for signal plausibility. If plausibility errors are detected between pot No. 1 and pot No. 2, ME 7.2 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 ME 7.2 uses the air mass signalling as a virtual potentiometer (pot No. 3) for a comparative source to provide failsafe operation. If ME 7.2 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 motor is initially switched on as a pre-flight check to verify its mechanical integrity (no binding, appropriate return spring tension, etc). This is accomplished 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, however, continue to run extremely rough at idle speed. When a replacement EDK is installed, the ME 7.2 adapts to the new component (required amperage draw for motor control, feedback pot tolerance differences, etc). This occurs immediately after the next cycle for approximately 30 seconds. During this period of adaptation, the maximum opening of the throttle plate is 25 percent.

Siemens is an engine management system which meets the needs of Low Emission Vehicle (LEV) compliancy and is also OBD II compliant. This system also includes control of the Motor-Driven Throttle Valve (MDK). The PCM uses a pc-board single-processor control unit in the new SKE housing. E-box is located next to brake master cylinder. The Siemens PCM is flash programmable as are previous systems. PCM hardware includes

1. Modular plug connectors featuring 5 connectors in the SKE housing with 134 pins.
2. Connector 1 = Supply voltages and grounds.
3. Connector 2 = Peripheral signals (oxygen sensors, CAN, etc.).
4. Connector 3 = Engine signals.
5. Connector 4 = Vehicle signals.
6. Connector 5 = Ignition signals. Special features include 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. A new PCM must be installed if necessary.

Ignition System

Siemens system uses a multiple spark ignition function. The purpose of multiple ignition is to 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 long-life plugs). 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 equals less multiple ignitions, high battery voltage equals more multiple ignitions.

Motor Driven Throttle Valve

The MDK control function has been integrated into the PCM. The purpose is for precision throttle operation, OBD II compliant for fault monitoring, ASC/MSR control, and cruise control. This integration reduces extra control modules, wiring, and sensors. The MDK control function is integrated into the Siemens PCM. The PCM carries this function out by regulating the engine throttle valve. The engine throttle valve performs precision intake air control.

The new engine throttle valve (MDK) differs from the familiar EML in that the accelerator pedal potentiometer (PWG) is now integrated in the MDK housing and a throttle cable is used to actuate the throttle potentiometers and also serves as a back-up to open the throttle plate (full control) if the MDK system is in failsafe. The throttle cable (foot pedal controlled) is connected to a pulley on the side of the MDK. The pulley is linked by springs to one end of the throttle shaft, the MDK electric motor is attached to the other end of the throttle shaft. (Scheme 8)

With the pulley linked by springs to the throttle shaft, this allows ASC intervention to override the driver's set throttle position. As the pulley and shaft are rotated, the twin potentiometers (integral in the MDK housing) are sensing the requested load. A twin potentiometer is used for back up redundancy (failsafe). The PCM will actuate the MDK motor pulse width modulated in both directions (at a basic frequency of 600 Hz) which positions the throttle plate. The second twin potentiometers feedback the actual throttle plate position, allowing the PCM to verify correct throttle position. Again, twin potentiometers are used for back up redundancy (failsafe).

Scheme 8

MDK Emergency Operation

If a fault is detected in the system, the modes of operation are emergency operation 1 and emergency operation 2.

Emergency operation 1 involves activation of the EML warning lamp, MDK deactivated, the throttle valve is opened mechanically by the springs and throttle cable, MDK opening is compensated for by closing the idle speed actuator and retarding the ignition (engine power reduction) and engine power is further limited by fuel injector cutout. Emergency operation 1 limits the dynamic operation if one or more of the potentiometers fail. The engine can slowly reach maximum speed with limited power. The EML light will be illuminated to alert the driver of a fault.

If another fault is encountered in addition to emergency operation 1 or if the plausibility is affected, emergency operation 2 is activated by the PCM. An example of plausibility fault would be that the pulley position does not match the MDK position and the associated airflow. Emergency operation 2 can also be initiated by simultaneously pressing both the accelerator pedal and the brake pedal, or if a fault is encountered in the brake light switch diagnosis. When in emergency 2 operation mode, there is an engine speed limitation (slightly above idle speed) in addition to the measures for emergency operation 1. In emergency operation 2, the engine speed is always limited to 1300 RPM if the brake is not applied, and approximately 1000 RPM if the brake is applied. The vehicle speed is limited to approximately 20-25 mph. The reason for limiting the vehicle speed is if the MDK is wide open and vacuum assist is insufficient for the brakes. The emergency operation functions are inactive when ignition is switched off, main relay is deactivated, and engine is started again.

MDK safety concept can detect a jammed or binding throttle valve as well as a broken link spring. This fault is detected by the PCM monitoring the feedback potentiometers from the MDK in relation to pulse width modulation to activate the MDK motor. Emergency operation functions if the throttle valve is jammed. In the event of a fault, the DIS or MoDiC must be used to interrogate the fault memory, and clear the fault once the proper repair has been performed.

Electronic Throttle Control (EDR) S62 Engine

The electronic throttle control system (EDR) was developed specifically for the S62 engine. The design criteria was to develop an EML system capable of actuating the eight throttles while ensuring that the power potential of the S62 engine was not compromised. The three main components of the system include the pedal position sensor (PWG), EDR motor, and MS S52 engine control system which is responsible for operation and monitoring of the throttle control system. The pedal position sensor is the driver's input for increased torque output of the engine. The PWG input is processed by the MS S52 control module. Plausibility checks are carried out and the EDR motor is operated to open the throttle valves. All eight throttle valves are opened simultaneously through the linkages connected to the EDR. The system requires approximately 120 ms to fully open the closed throttle valves. Feedback of the current throttle valve position is achieved through 2 throttle valve potentiometers located on the ends of the throttle valve shafts.

PWG provides 2 separate variable voltage signals to the MS S52 control module for determining the request for EDR operation. The MS S52 monitors the changing signal ranges of both circuits as the pedal is pressed from idle to full throttle. PWG Pot No. 1. is 0.5-4.5 volts. PWG Pot No. 2 is 0.5-2.0 volts. PWG pot signal No. 1 is the primary input for throttle opening request. The signal from Pot No. 2. is used primarily for plausibility checking. If the signal ranges are incorrect, MS S52 will activate an emergency operating program based on the specific fault recognized.

As a safety check, a pre-drive check of the EDR system is carried out every time the ignition is switched on. MS S52 control module briefly opens the throttles and checks zero set point of the feedback potentiometers, free movement of the throttle valves, operation of the EDR actuator motor, and operation of the return springs in the EDR actuator motor.

There are a total of 4 emergency operation programs stored in the MS S52 control module. The MS S52 control module will activate one of these programs depending on which fault is present or what component failed. With any fault that is relevant to the EDR system, the engine's output torque will be reduced to provide limited driveability of the vehicle.

Emergency program No. 1 is engine operation with PWG input. The engine's output torque is limited to 480 Nm. This program will set with faults in one PWG sensor input or one throttle valve feedback input.

Emergency program No. 2 is engine operation through the idle valve actuator. The engine's output torque is limited to 300 Nm and the vehicle's speed to 70 MPH. With program No. 2, the throttle valves are shut down and only the idle valve is used for engine operation. This program will set with a fault in one air mass sensor input and one PWG sensor input.

Emergency program No. 3 is engine operation with jammed throttle valves. The engine's output torque is limited to 300 Nm and the speed is limited to 35 MPH. This is carried out through ignition and injection intervention if the MS S52 senses that the throttle valves are jammed or stuck and cannot be closed by applying power through the EDR actuator.

Emergency program No. 4 is engine operation with a control module internal fault. The engine's output torque is limited to 250 NM and the speed is limited to 35 MPH. Depending on the degree of the fault, the control module with the dual processors will enable limited engine operation.

Idle Control System (ZWD 5) S62 Engine

Idle control on the S62 engine is carried out using the ZWD 5 idle control valve. The valve features a second air supply system that functions independently from the throttle control system. The idle valve draws in metered air from the intake plenum and it is connected to both sets of throttle valves though an interconnected pipe. The valve receives power from the main relay and the open and close windings are controlled by the MS S52 control module. Without power, the valve is open approximately 30 percent. Under certain conditions, the idle control valve can be opened by the control module to provide air flow for emergency (limp home) operation.

INPUT DEVICES (ALL SYSTEMS)

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine input device usage for a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available input signals include the following

Malfunction Indicator Light (MIL)

See SELF-DIAGNOSTIC SYSTEM .

Fuel Injectors

See FUEL CONTROL under FUEL SYSTEM.

Fuel Tank Vent (Evaporation) Control

See EMISSION SYSTEMS .

Fuel Pump Relay

See FUEL DELIVERY under FUEL SYSTEM.

Idle Speed Actuator

See IDLE SPEED under FUEL SYSTEM.

Ignition Timing & Anti-Knock Function

See DIRECT IGNITION SYSTEM (DIS) under IGNITION SYSTEMS.

Ignition Timing Control

See IGNITION SYSTEMS .

Kickdown Prevention

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

INPUT DEVICES (MOTRONIC)

Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation on each output component, refer to system indicated after component.

Accelerator Pedal Sensor (PWG)

The driver's application of the accelerator pedal is monitored by a PWG sensor in the driver's footwell as with previous non-bowden cable EML systems. The PWG provides 2 separate variable voltage signals to the ME 7.2 control module for determining the request for operating the Electric Throttle Valve (EDK) as well as providing a kickdown request with automatic transmission vehicles. The ME 7.2 monitors the changing signal ranges of both circuits as the pedal is pressed. (Scheme 9)

In vehicles equipped with an automatic transmission (A5S 440Z), the ME 7.2 recognizes the max pedal value (4.5V) as a kickdown request and signals the AGS via CAN bus. If the monitored PWG potentiometer signals are not plausible, ME 7.2 will only use the lower of the 2 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, ME 7.2 sets the EDK throttle plate and injection time to idle 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 9

Brake Light Switch

The Electronic Brake Switch (Hall effect) provides brake pedal position status to the ME 7.2. The control module monitors both the brake light and a separate brake light test switch circuits for plausibility. When the brake pedal is pressed, the brake light segment of the switch provides a high signal. Simultaneously, brake light test switch (located in same housing) provides a ground signal.

Camshaft Position Sensors

Located on upper timing case covers, camshaft position sensors monitor position of camshafts to establish start of ignition firing order, set up sequential fuel injection triggering and for accurate camshaft advance-retard (VANOS) timing feedback. Each intake camshaft's advance-retard angles are adjusted simultaneously yet independently. For this reason ME 7.2 requires a camshaft position sensor on each cylinder bank for accurate feedback to monitor the VANOS controlled camshaft positioning. The sensors are provided with operating power from the PCM main relay. The sensors produce a unique asymmetrical square-wave signal representative of the impulse wheel shape. The sensors are new in the fact that they are "active" hall effect sensors. Active hall sensors provide low signal when a tooth of the camshaft impulse wheel is located in front of the sensor and high signal when an air gap is present. The active hall sensors supply a signal representative of camshaft position even before the engine is running. The ME 7.2 determines an approximate location of the camshafts positions prior to engine start up optimizing cold start injection (reduced emissions.) (Scheme 10)

Scheme 10

Cruise Control Data Signal

The ME 7.2 control module provides cruise control function. Throttle activation is provided by ME 7.2 automatic control of the EDK and monitoring of the throttle plate position feedback potentiometer signals. All of the familiar driver requested cruise control function requests are provided to the ME 7.2 control module via the MFL control module on a single data signal wire

EDK Throttle Position Feedback Signals

The EDK throttle plate position is monitored by 2 integrated potentiometers (pot). The potentiometers provide DC voltage feedback signals as input to the ME 7.2 for throttle and idle control functions. Potentiometer signal No. 1 is the primary signal. Potentiometer signal No. 2 is used as a plausibility cross-check through the total range of throttle plate movement. (Scheme 11)

If plausibility errors are detected between pot 1 and pot 2, ME 7.2 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 ME 7.2 uses the air mass signalling as a virtual potentiometer (pot 3) for a comparative source to provide failsafe operation. If ME 7.2 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-check to verify its mechanical integrity (no binding, appropriate return spring tension) by monitoring 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 continue to run extremely rough at idle speed.

Scheme 11

Electronic Throttle Valve (EDK) Control

The throttle valve assembly of the M62 TU is an electric throttle valve (EDK) controlled by an integral EML function of the ME 7.2. The throttle plate is positioned by a gear reduction DC motor drive. The motor is controlled by proportionately switched high/low PWM signals at a basic frequency of 2000 Hz. Engine idle speed control is a function of the EDK. Therefore, the M62 TU does not require a separate idle control valve. When a replacement EDK is installed, the adaptation values of the previous EDK must be cleared from the ME 7.2 control module.

From the Service Function Menu of the DIS/MoDiC, clear adaptation values. Switch the ignition OFF for 10 seconds. Switch the ignition ON. At approximately 30 seconds the EDK is briefly activated allowing the ME 7.2 to electrically learn the new component. This procedure is also necessary after replacing an ME 7.2 control module. However, the adaptation values do not require clearing since they have not yet been established.

Hot Film Air Mass Sensor

The M62 TU is equipped with a new Hot Film Air Mass Sensor identified as HFM 5. It is a combined air mass/intake air temperature sensor. The separate intake air temperature sensor is no longer used on the M62 TU. The HFM 5 is provided with operating power from the PCM main relay. Based on calculated intake air mass, the HFM 5 generates a varying voltage between 0.5 and 4.5 volts as an input signal to the ME 7.2. An additional improvement of the HFM 5 is that the hot film element is not openly suspended in the center bore of the sensor as with previous HFMs. It is shrouded by a round fronted plastic labyrinth which isolates it from intake air charge pulsations. This feature allows the HFM to monitor and calculate the intake air volume with more accuracy. This feature adds further correction for calculating fuel injection ON time which reduces emissions further. (Scheme 12)

Scheme 12

Integrated Ambient Barometric Pressure Sensor

The ME 7.2 Control Module contains an integral ambient barometric pressure sensor. The sensor is part of the SKE and is not serviceable. The internal sensor is supplied with 5 volts. In return it provides a linear voltage of approximately 2.4 to 4.5 volts representative of barometric pressure (altitude). The ME 7.2 monitors barometric pressure because pressure signal along with calculated air mass provides an additional correction factor to further refine injection ON time and it provides a base value to calculate the air mass being injected into the exhaust system by the secondary air injection system. This correction factor alters the secondary air injection ON time, optimizing the necessary air flow into the exhaust system. (Scheme 13)

Scheme 13

Radiator Outlet Temp Sensor

First seen on the MS 42.0 control system, the ME 7.2 uses an additional water temperature sensor located on the radiator outlet. ME 7.2 requires this signal to monitor the water temperature leaving the radiator for precise activation of the IHKA auxiliary fan. (Scheme 14)

Scheme 14

DSC III - Road Speed Signal

ME 7.2 receives the road speed signal directly from the DSC III control module for maximum vehicle speed management. The DSC control module provides a processed output of the right rear wheel speed sensor as a digital square wave signal. The frequency of the signal is proportional to the speed of the vehicle (48 pulses per one revolution of the wheel). The cruise control function (FGR) of the ME 7.2 also monitors vehicle speed from the redundant vehicle speed CAN bus signal. The CAN bus speed signal is provided by the DSC III control module and based on the combined average of both front wheel speed signals. Additionally, ME 7.2 monitors all four wheel speed signals via CAN bus signalling to detect abrupt fluctuations in vehicle speed signals for the purpose of detecting rough road surfaces. This is continuously monitored as part of the OBD-II emission requirements providing a correction factor for misfire detection plausibility. Earlier systems only monitored the right rear speed signal input from DSC. (Scheme 15)

Scheme 15

INPUT DEVICES (SIEMENS SYSTEM)

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine input device usage for a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available input signals include the following

Camshaft Sensors

Static Hall sensors are used so camshaft positions are recognized once ignition is on, even before the engine is started. The function of the intake camshaft sensor is cylinder bank detection for preliminary injection, synchronization, engine speed sensor (if crankshaft speed sensor fails), and position control of the intake cam (VANOS). The exhaust camshaft sensor is used for position control of the exhaust camshaft (VANOS). If these sensors fail there are no substitute values. System will operate in the failsafe mode with no VANOS adjustment. The engine will still operate, but torque reduction will be noticeable. (Scheme 16)

Scheme 16

Located on the rear of the cylinder head, the camshaft position sensors (Hall effect) monitor the position of the camshafts to establish start of ignition firing order, setup sequential fuel injection triggering and for accurate camshaft advance and retard (double VANOS) timing feedback. With full variable VANOS control on both the intake and exhaust camshafts, four camshaft position sensors are required. The sensors are provided with operating power from the PCM main relay and produce a square wave input signal to the PCM. The trigger wheels contain a wide tooth that is used to establish full sequential injection.

Catalytic Converter Temperature Monitoring

Some vehicles are equipped with an exhaust temperature sensor at the catalyst for cylinder banks No. 5-8. The sensor is a PTC resistor which allows the MS S52 to monitor the catalyst temperature. This input is considered for mixture control by the MS S52 for catalyst efficiency. In the event of an overheat situation, the PCM will illuminate the Malfunction Indicator Light (MIL) and set a fault code. Under certain load conditions, the fuel mixture is enriched to aid in cooling down the catalytic converters.

Crankshaft Sensor

Crankshaft sensor is a dynamic Hall-effect sensor mounted through the engine block. Signal is sent the moment the crankshaft begins to rotate. The pulse wheel is mounted directly to the crankshaft. (Scheme 17)

Scheme 17

Crankshaft Position Sensor

The engine speed (RPM) and crankshaft position input signals are provided by the inductive pulse sensor that scans the incremental gear wheel mounted on the flywheel of the engine. Operation of this sensor is the same as other M5.x systems. The rotation of the gear wheel generates an A/C voltage signal in the sensor where each tooth of the wheel produces one pulse. The engine control module counts these pulses and determines engine speed and crankshaft position. The signal from the crankshaft sensor is also used for OBD II monitoring for misfire detection. (Scheme 18)and (Scheme 19).

Scheme 18

Scheme 19

Engine Coolant Temperature Sensor

The engine coolant temperature (NTC) input to the control module is used to provide enrichment for cold starts and cold engine running conditions. The sensor is located near the thermostat housing. The oil temperature sensor input is used as a replacement value in the event of a failure with the coolant temperature sensor input.

The MS S52 system uses the hot film air mass sensor for measuring the air intake volume. Two air mass sensors are used with the M5 engine to ensure that an sufficient volume of air can enter the engine under full load operating conditions. The operation of the hot film air mass sensor remains the same as previous systems. The sensor receives operating power from the PCM relay.

Intake Air Temperature

Intake air density (temperature) for injection is automatically compensated for by the air mass sensors. However, an additional air temperature (NTC) function is required for ignition timing. The sensing function is integrated into the driver's side air mass meter and provides a signal dependent on air temperature.

The MS S52 control module contains an integral ambient barometric pressure sensor. The sensor is part of the SKE and is not serviceable. The internal sensor is supplied with 5 volts. In return, the sensor provides a linear voltage of approximately 2.4 to 4.5 volts representative of barometric pressure (altitude). The barometric pressure signal along with calculated air mass provides an additional correction factor to further refine injection on time, and provides a base value to calculate the air mass being injected into the exhaust system by the secondary air injection system. This correction factor alters the secondary air injection on time, optimizing the necessary air flow into the exhaust system. Recognition of altitude above the accepted criteria postpones DM-TL activation for evaporative emission leak diagnosis.

Knock Sensors

The use of knock sensors allows control module to maintain the optimum ignition timing curve for all engine operating conditions. If detonation occurs, the signal from the knock sensors allow the engine control module to retard the timing to prevent engine damage. Each knock sensor produces a varying voltage signal that is dependent on the level of noise produced by the cylinders. This voltage signal input is processed by the control module and if the level exceeds the programmed parameters for knock, the timing is retarded until the knock is eliminated.

Mass Air Flow Sensor

Sensor is located in intake passage between air filter and intake manifold. Sensor informs PCM of airflow rate.

Misfire Detection

As part of CARB/OBD regulations, 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/engine roughness calculation is derived from the differences in the period duration of individual increment gear segments. Each segment period consists of an angular range of 120 degree crank angle that starts 78 degrees 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 DME. Depending on the level of misfire rate measured, the control unit will illuminate the CHECK ENGINE light, may cut-off 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.

Oil Temperature/Level Sensor

The electronic level sensor is located in the engine sump mounted to the engine oil pan. The probe of the level sensor contains 2 temperature sensing elements. One senses engine oil temperature. The other is heated to 50°F (10°C) above the temperature of the engine and then is allowed to cool. The length of time it takes to cool the heated element is how the sensor determines the engine oil level. When the oil level is high it covers a larger portion of the probe submersed in the oil sump. The engine oil around the probe absorbs the heat of the heated element quicker than if the level is low. The microprocessor in the base of the sensor produces a pulse width modulated signal proportional to the oil level. The pulse width decreases with a decreased level of oil. The MS S52 control module uses the oil temperature input signal to protect the engine during cold engine warm-up. Based on the oil temperature, the visual warning LEDs in the tachometer will illuminate at cold engine start up and slowly be extinguished as the oil temperature increases. The oil temperature sensor also serves as a vital input for VANOS operation, varying the solenoid control based on oil temperature (reaction time of camshaft movement). In the event of a fault the engine coolant temperature is used as a substitute value.

Oxygen Sensors

System uses Bosch oxygen sensors. Voltage range is 0-800 mV. Pre-cat sensors are mounted on top of the exhaust manifolds. Catalysts are integral with the exhaust manifolds.

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 PCM to trim the 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. 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 injection time to compensate for this. The constantly changing oxygen sensor input to the PCM is needed to correct the injection time to ensure the ideal air/fuel ratio is maintained.

Power Transmission Switch

The power transmission switch (circuit) consists of 2 switches in series. The circuit includes a clutch switch and a gear selector switch on the transmission. The functions of the power transmission switch are cutout for cruise control operation and enable condition for idle control. The switches provide a high signal for the MS S52 when the clutch is disengaged and the transmission is in gear. If either the clutch is engaged or the transmission is in neutral, the cruise control will be disengaged. In addition, this circuit arms the MS S52 to apply torque reduction during hard acceleration and gear changes. This feature is basically accomplished by reducing the throttle openings if the PWG request signal is not reduced during gear changes.

Throttle Progression Switch

The MS S52 control system contains 2 different throttle progression program curves (sport and normal). The sport program is selected by pressing the sport switch located in the center console switch panel. The switch provides a ground signal as an input when pressed. The MS S52 activates the sport characteristics for the EDR throttle control. This provides an increase in throttle opening over the non-sport position. At the same time the ZKE control module is signaled over the CAN and K-Bus to activate the sport servotronic (increased road feel) steering characteristic program.

OUTPUT SIGNALS (MOTRONIC)

Vehicles are equipped with different combinations of output devices. Not all devices are used on all models. To determine output device usage for a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available output devices include the following

Fuel Pump Relay Control

ME 7.2 controls the fuel pump relay as with previous systems with regard to engine speed input for continual activation of the relay. The ME 7.2 will switch off the fuel pump relay when an air bag is activated as an additional safety function. The signal is passed from the MRS III control module to the ME 7.2 over the CAN line. (Scheme 20)

Scheme 20

"E" Box Fan Control

The "E" box fan is controlled by ME 7.2. The control module contains an integral NTC temperature sensor for the purpose of monitoring the "E" box temperature and activating the fan. When the temperature in the "E" box exceeds predetermined values, ME 7.2 provides a switched ground for the "E" box fan to cool the "E" box located control modules. With every engine start-up, ME 7.2 briefly activates the fan ensuring continued fan motor operation for the service life of the vehicle. This feature is intended to prevent fan motor lock up from lack of use due to pitting or corrosion over time.

Secondary Air Injection

Secondary air injection is required to pre-heat the catalytic converters for OBD II compliance. The DME ME7.2 control unit controls the vacuum vent valve and the secondary air injection pump relay separately but simultaneously. The secondary air pump operates at a start temperature of between 50-104°F (10-40°C). It continues to operate for a maximum of 2 minutes at idle speed. ME 7.2 contributes an additional correction factor for secondary air "on" time with the additional input from the integral ambient barometric pressure sensor. This sensor provides a base value to calculate the air mass being injected into the exhaust system. This helps to "fine tune" the secondary air injection "on" time, optimizing the necessary air flow into the exhaust system which reduces the time for catalytic converter light-off.

Throttle valve assembly of the M62 TU is an electric throttle valve (EDK) controlled by an integral EML function of the ME 7.2. The throttle plate is positioned by a gear reduction DC motor drive. The motor is controlled by proportionately switched high/low PWM signals at a basic frequency of 2000 Hz. Engine idle speed control is a function of the EDK. Therefore, the M62 TU does not require a separate idle control valve.

When a replacement EDK is installed, adaptation values of the previous EDK must be cleared from the ME 7.2 control module. From the Service Function Menu of the DIS/MoDiC, clear adaptation values. Switch the ignition OFF for 10 seconds. Switch the ignition ON. At approximately 30 seconds, EDK is briefly activated allowing ME 7.2 to "electrically learn" the new component. This procedure is also necessary after replacing an ME 7.2 control module. However, the adaptation values do not require clearing since they have not yet been established.

Auxiliary Fan Control

Auxiliary fan motor incorporates an output final stage that activates the fan motor at variable speeds. The auxiliary fan is controlled by ME 7.2. The motor output stage receives power and ground and activates the motor based on a PWM signal (10-100 Hz) received from the ME 7.2. Similar to the auxiliary fan in the E46 with MS 42.0 control, the fan is activated based on radiator outlet temperature sensor input exceeds a preset temperature, IHKA signalling via the K and CAN bus based on calculated refrigerant pressures, vehicle speed and battery voltage level. (Scheme 21) When the over temperature light in the instrument cluster is on 248°F (120°C), the fan is run in the overrun function. This signal is provided to the DME via the CAN bus. When this occurs the fan is run at a frequency of 10 Hz.

Scheme 21

OUTPUT SIGNALS (SIEMENS SYSTEM)

Note. Vehicles are equipped with different combinations of output devices. Not all devices are used on all models. To determine output device usage for a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available output devices include the following

The auxiliary fan motor incorporates an output final stage that activates the fan motor at variable speeds. The auxiliary fan is controlled by the MS S52. The motor output stage receives power and ground and activates the motor based on a PWM signal (10-100 Hz) received from the MS S52. Similar to the auxiliary fan in the E46 with MS 42.0 control, the fan speed or activation is based on radiator outlet temperature sensor input exceeds a preset temperature, IHKA signalling via the "K" and CAN bus based on calculated refrigerant pressures, vehicle speed and battery voltage level. When the over temperature light in the instrument cluster is on 248°F (120°C) the fan is run in the overrun function. This signal is provided to the PCM via the CAN bus. When this occurs the fan is run at a frequency of 10 Hz. (Scheme 21)

Electric Fan

Electric cooling fan is now controlled by the PCM. PCM uses a remote power output final stage mounted on fan housing. The power output stage receives power from a 50-amp fuse (located in glove box above fuse bracket). Electric fan is controlled by a pulse width modulated signal from the PCM. The fan is activated based on the PCM calculation (sensing ratio) of coolant outlet temperature, calculated (by the PCM) catalyst temperature, vehicle speed, battery voltage, and air conditioning pressure.

When vehicle is first started the fan is activated briefly (20 percent of maximum speed), then it is switched off. This procedure is performed for diagnostic purposes. If PCM indicates a fault, check fan for freedom of movement. After initial test has been performed, fan is brought up to specified operating speed. At 10 percent (sensing ratio) fan runs at 1/3 speed. At a sensing ratio of between 90-95 percent the fan is running at maximum speed. Below 10 percent or above 95 percent the fan is stationary. When 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 PCM calculated catalyst temperature).

The "E" Box fan is controlled by the MS S52. The control module contains an integral NTC temperature sensor for the purpose of monitoring the "E" box temperature and activating the fan. When the temperature of the "E" box exceeds predetermined values, MS S52 provides a switched ground for the "E" box fan to cool the "E" box located control modules. With every engine start-up, MS S52 briefly activates the fan ensuring continued fan motor operation for the service life of the vehicle. This feature is intended to prevent fan motor "lock up" from lack of use.

Engine/Vehicle Speed Limitation

For engine/vehicle speed limitation, PCM will deactivate injection for individual cylinders, allowing a smoother limitation transition. This prevents over-rev when engine reaches maximum RPM (under acceleration), and limits top vehicle speed (approximately 128 mph).

Fuel Circuit Changeover

Fuel circuit changeover (running losses) has not changed in operation from the previous system. The attached fuel pressure regulator no longer controls fuel pressure influenced by vacuum supply. PCM now determines fuel quantity compensation for manifold vacuum changes. This is based on throttle position sensor, air mass meter, load, etc., for precise compensation. Maintained fuel pressure at fuel distribution rail is a constant 51 psi (3.5 bar). Vacuum line no longer connects to intake manifold vacuum, but is routed to crankcase cyclone separator (in case of regulator diaphragm leakage).

Fuel injectors inject at an angle (dual cone spray pattern). Tip of injector is fitted with a directional angle plate with dual outlets. Lower portion of injector body is jacketed in metal.

For engine/vehicle speed limitation, PCM will deactivate injection for individual cylinders, allowing a smoother limitation transition. This prevents over-rev when engine reaches maximum RPM (under acceleration), and limits top vehicle speed.

Injector Control

The MS S52 control module calculates the correct injection time based on the control parameters of engine speed, air mass, throttle position, oxygen sensor feedback signal, engine coolant, barometric pressure and battery voltage. The injectors receive operating power from the main relay and the control module provides the ground for the duration of the injection time.

Fuel Pump Module

The MS S52 controls the activation of the fuel pump module. After the ignition is switched ON the control module provides a pulse width modulated ground for the relay and the ground is maintained with the presence of the engine speed signal. A new fuel pump is utilized to match the fuel supply demands of the S62 engine. While the pump delivers more volume and pressure, this creates more heat due to the increased power consumption. To lower the in-tank temperature, the fuel pump module will vary the pump speed (amperage). The MS S52 control module will vary the ground signal (PWM) to the fuel pump module. This variation is based on engine speed and load. The power to the fuel pump relay will be switched off in the event of an air bag activation. The MRS III control module will signal the engine control module over K-bus and CAN bus for this purpose.

Idle Control Valve

The S62 engine uses an idle control valve for idle stabilization. During idle conditions, the throttle valves are closed and all idle air passes through the idle valve. The valve on S62 engine is 3-wire ZWD 5 system. The valve has 2 windings that oppose each other. By varying the duty cycle applied to the windings, the valve can be progressively opened, closed or held steady to maintain the idle at a specified speed. The valve has a mechanical fail-safe opening of 30 percent which will allow the engine to idle in the event of a malfunction with the control of the valve. The idle control valve also serves as a fail-safe in the event of certain faults with the throttle control system (EDR). MS S52 control module can progressively open the valve to allow limited operation of the engine.

Ignition Coil Triggering

Control of ignition coils is an output function of MS S52 control module. System is solid state with no moving parts. Control module triggers each coil individually based on parameters of engine speed and crankshaft position. Ignition timing can be modified between each individual coil firing and can also be adjusted on a cylinder selective basis for knock control.

Main Relay Control

The MS S52 control module activates the main relay. This provides operating power for the control module and traction control module, fuel pump relay, secondary air pump relay/air pump, E-box cooling fan, auxiliary oil pump solenoids, purge valve, fuel injectors, VANOS solenoids, oxygen sensor heaters, air mass sensors, and idle control valve. The MS S52 maintains the ground for the main relay for a short duration after the ignition has been switched off. This allows the control module to store the adaption values and any fault codes.

Non Return Fuel Rail System

The S62 engine utilizes the same method of meeting running loss compliance as previously seen on the M62 TU. The regulated fuel supply is controlled by the fuel pressure regulator integrated in the fuel filter assembly (pressure testing tap at this point). A fuel return line is located on the filter/regulator assembly. The system provides even fuel distribution to all fuel injectors due to a "T" connection feeding both fuel rails. The new fuel rails do not contain a return line.

Oil Sump Changeover Valves

The oil supply system of the S62B50 engine is specifically designed for the M5, due to its ability for high speed cornering that could cause the engine oil to be forced (and trapped) into the outer edge of the cylinder head and the rear area of the oil sump. To prevent oil starvation from occurring during these driving situations, 2 additional scavenging oil pumps are installed within the main oil pump housing. The main oil pump's function supplies the engine with the required volume of oil for all of its lubrication needs. The 2 additional pumps only supply oil sump with scavenged oil. Each additional oil pump incorporates a solenoid changeover valve that is connected to 2 scavenging tubes that pickup from the rear section of the oil pan and the outer edge of the cylinder head. The scavenging tubes in oil pan crossover so right side pump draws from rear left side of pan and left pump from right side of pan. MS S52 control module receives "G" force signal from DSC control module over CAN line.

Oxygen Sensor Heating

Oxygen sensor heating is an output function of the MS S52 control module. The heating circuits receive operating power from the main relay. Each of the heaters is controlled through a separate final stage which is monitored by the control module for OBD II purposes. The heaters are controlled with a pulsed square wave voltage during cold start which allows heating to occur without the result of thermo-shock. The duty cycle is then varied to maintain the heating of the sensors. On decel, the duty cycle will be increased to maintain the heating of the sensors during closed throttle operation with fuel cut.

Purge Control Valve

The MS S52 system uses a purge valve that is sprung closed and powered open. This type of purge valve is required for OBD II compliancy and evaporative system leak detection tests. This type of valve also prevents vapors escaping into the atmosphere when the vehicle is not in use. The valve will not open under fuel vapor over pressure. The valves are cycled periodically during engine operation. The duty cycle of the purge valve solenoid may vary between 0-100 percent depending on engine operating conditions. Evaporative purge system is monitored for flow check after fuel system adaptation is complete and PCM oxygen sensor feedback is in closed loop. The diagnosis starts during normal purge operation. After the system has completed a purge cycle, the valve is cycled abruptly several times. In addition to the rich/lean shift, the engine idle speed will vary. If the predetermined values are reached, the system is functioning properly. The flow check will operate after oxygen sensors in closed loop, engine at idle speed and coolant temperature above set limit.

Resonance/Turbulence Intake System

On M52 TU, intake manifold is split into 2 groups of 3 runners which increases low end torque. Intake manifold also has separate internal turbulence bores which channels air from idle speed actuator directly to one intake valve of each cylinder. Routing the intake air to only one intake valve causes intake to swirl in cylinder. Together with high flow rate of intake air due to small intake cross sections, this results in a reduction in fluctuations and more stable combustion.

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 intake manifold controlled by PCM. During low to mid range RPM, resonance flap is closed. This produces a long/single intake tube for velocity, which increases engine torque. During mid range to high RPM, resonance flap is open. This allows intake air to pull through both resonance tubes, providing air volume necessary for additional power at upper RPM range. When the flap is closed , this creates another dynamic effect. For example, as intake air is flowing into cylinder No. 1, intake valves will close. This creates a roadblock for inrushing air. The airflow will stop and expand back (resonance wave back pulse) with inrushing air to cylinder No. 5. The resonance wave, along with intake velocity, enhances cylinder filling. PCM controls a solenoid valve for resonance flap activation. At speeds below 3750 RPM, solenoid valve is energized and vacuum supplied from an accumulator closes resonance flap. This channels intake air through one resonance tube, but increases intake velocity. When engine speed is greater than 4100 RPM, solenoid is de-energized. Resonance flap is sprung open, allowing flow through both resonance tubes, increasing volume.

RZV Ignition System

Siemens MS42.0 system uses a multiple spark ignition function known as RZV ignition. The purpose of multiple ignition is to 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. 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 voltage is low, primary current is also lower and a longer period of time is required to build up magnetic field in coil(s). Low battery voltage equals less multiple ignitions. High battery voltage equals more multiple ignitions. A 240-ohm shunt resistor is used on MS42.0 system for detecting secondary ignition faults and diagnostic purposes. (Scheme 22)

Scheme 22

Air injection inlet valve mounts directly to cylinder head, with a passageway machined through the head. This eliminates the external air injection manifold distribution pipes to the exhaust manifolds. To reduce HC and CO emissions while engine is warming up, BMW implemented the use of a Secondary Air Injection System. Immediately following a cold engine start -10°F (-40°C) fresh air/oxygen is injected directly into exhaust manifold.

By injecting oxygen into exhaust manifold, warm up time of catalyst is reduced and oxidation of hydrocarbons is accelerated. Activation period of the air pump can vary depending on engine type and operating conditions. For conditions for secondary air pump activation, see SECONDARY AIR PUMP STATUS/CONDITION table.

SECONDARY AIR PUMP STATUS/CONDITION

Fuel Pump

All vehicles use an in-tank electric fuel pump, accessible through luggage compartment or rear bench seat. Fuel pump is activated by voltage supplied by fuel pump relay.

Fuel pump relay is powered through master (main) relay and positive battery junction point "B" and is grounded through PCM terminal No. 1.

Master Relay (DME Relay)

Master relay is powered through positive battery junction point "B" and supplies power to PCM, Heated Oxygen Sensor (HO2S), fuel pump relay and other computer-controlled systems.

Fuel Pressure Regulator

Pressure regulator maintains constant fuel pressure to injectors. An electric fuel pump provides fuel to pressure regulator. Pressure regulator is vacuum operated. As throttle is depressed and manifold vacuum drops, pressure regulator increases fuel pressure to maintain constant flow to fuel injectors.

Control of the fuel pump relay is an output function of the PCM. The main relay provides operating power for the fuel pump relay. After the initial ignition ON input, the PCM provides a ground for the fuel pump control circuit. The circuit is maintained with the presence of the engine speed signal. The fuel pump relay supplies operating power to the in-tank mounted fuel pump.

All systems except V12 engine systems use a single submersed (in fuel tank) fuel pump. The V12 configuration consists of 2 redundant fuel supply systems. The pump primes the system when the ignition is switched on, and will run continuously when the engine control module senses engine RPM via the crankshaft position sensor. The pump supplies constant fuel volume to the injection system. The pickup for the pump is protected by a mesh screen.

Fuel pressure regulator maintains a constant pressure differential for the fuel injectors. Pressure is set by the internal spring tension (approximately 2.5-3.5 bar). The lower chamber is sealed off by a diaphragm. It is connected to a manifold vacuum hose. Intake manifold vacuum influences the pressure compensation to ensure pressure differential across the injectors remains constant. The internal valve (restriction) returns the unused fuel back to the fuel tank via the fuel return line.

Fuel pressure regulator at wide open throttle has depleted manifold vacuum at the tip of the injector (and also in the vacuum chamber of the pressure regulator), therefore the pressure behind the injector is increased due to the lack of vacuum aiding the opening of the diaphragm in the pressure regulator. The spring closes the restriction to raise the pressure. Part throttle has manifold vacuum available at the tip of the injector to help flow the fuel through. That same vacuum is supplied to the pressure regulator, compensating restriction to raise the pressure.

Running Losses

Running losses refers to the fuel vapors that can escape to the atmosphere during vehicle operation. The fuel tank is the major source of running loss vapors. The fuel pressure regulator with bypass solenoid is equipped on all vehicles. With the engine running, the volume of fuel flowing through the fuel rail is more than the engine can consume. The fuel passing through the fuel rail is heated by the engine and is returned to the tank. Using the bypass type regulator reduces the fuel heating thereby reducing the temperature of the fuel in the tank. This lowers the amount of vaporization that takes place.

Fuel Injection

Powertrain Control Module (PCM) calculates the correct injection timing on the basis of battery voltage, engine speed, air flow or air mass, oxygen sensor signal, engine temperature, and throttle position. (Scheme 23) The mixture is varied by the opening time (ms) of the fuel injectors. The vehicle battery voltage is taken into consideration in calculating the injection timing. With lower than normal battery voltage, the injectors must be activated earlier to get the valves open in time (dwell) for optimum injection timing. Fuel injectors are activated by the engine control module either individually, in groups or all at once (during starting). Activated all at once is parallel fuel injection. In groups is semi-sequential fuel injection. Individually is full sequential fuel injection.

Scheme 23

Parallel injection refers to simultaneous activation of all fuel injectors and takes place only when the cylinder reference point sensor (pulse generator) has supplied no signal since starting the engine. As soon as a signal is applied, system switches over to semi-sequential injection after the next deceleration phase. Each injector valve group is activated by one output stage (power transistor). This arrangement makes it possible to divide the injection cycle into cylinder groups (semisequential injection).

Semi-sequential injection, during engine speed of 600 RPM, fuel is injected once per 720 degrees of crankshaft rotation into one cylinder group. This facilitates precise metering of the quantity of fuel since the injector valves are not activated as often. It also enables limited engine operation in the even of failure of one group. Semi-sequential injection is only active when the PCM has received the cylinder ID signal during start-up. If the signal is not received after the engine is already running, the system remains in semi-sequential injection.

Fully sequential injection utilizes a separate final stage output transistor in the control module for each injector. Fuel is injected into the incoming air charge just prior to the intake valve opening. Power is supplied to all injectors from the main relay, and each injector is activated by its own final stage. The control module is programmed to activate the injectors once for every 2 revolutions of the crankshaft. Triggering is first established from the input signal of the speed/reference sensor. The signal from the cylinder ID sensor ensures that the injection charge is timed to the proper cylinder. When activated, each injector delivers the full amount of fuel required for each working cycle. Loss of the cylinder ID sensor will only affect the full sequential injection to the point that the injected charge of fuel may not be timed to each respective intake valve.

Cold Start Control

During the start phase, fuel is injected several times for each cylinder group per crankshaft revolution. The quantity of fuel is adjusted depending on engine temperature and engine speed. In addition, the injection timing is retarded at higher engine temperatures and at slower engine cranking speeds. For example, on 12-cylinder engine, after the engine has started (as of approximately 600 RPM), fuel is injected only once per revolution of the crankshaft and cylinder group. (Scheme 24) This means that during the first crankshaft revolution fuel is injected into cylinders No. 2, 4 and 6 simultaneously and during the second revolution into cylinders No. 1, 3 and 5. Cylinders No. 8, 10 and 12, and No. 7, 9 and 11 are supplied with fuel in the same way but offset by 60 degree crank angle.

Scheme 24

Speed Limitation

The DME limits the maximum engine speed by cutting out the injector valves. The Siemens control module will shut down individual cylinders as required to prevent an over-rev situation when the engine reaches the maximum rev limit or maximum vehicle speed (128 MPH). Just prior to the cut out point (engine or vehicle speed), the air fuel ratio is leaned out and the injectors are shut down individually as needed. (Scheme 25)

Scheme 25

Deceleration Fuel Cut-Out

To reduce fuel consumption, the deceleration fuel cut-out is activated when the throttle valve is closed and the engine speed is above approximately 1000-1200 RPM. The engine control module continues to cutout the injection and retard the ignition timing until the engine speed has dropped below the 1000-1200 RPM cut-in speed. At and below the cut in speed, fuel injection resumes and the ignition timing is advanced once again. The cut-in speed is dependent upon the engine temperature and the rate of deceleration. Fuel economy indicator provides a visual demonstration of this function. In the case of a sudden change in the throttle position towards the full load direction, the engine control module increases the quantity of injected fuel (ms time increased) for the duration of the request for acceleration and also advances the ignition timing. The engine control module provides the acceleration enrichment while also taking into account the criteria for maximum torque, emissions, detonation and knock sensor input. (Scheme 26)

Scheme 26

Catalytic Converter Protection

The catalytic converter protection feature is a function of the DME control module. The control module can cancel injector triggering, to prevent unburned fuel from entering the exhaust system, when there is a problem with the ignition system. The control module is programmed to selectively cancel the injector final stage output(s) based on processing and signals received from the ignition monitoring circuit. Depending on the version, various different monitoring and cancelling possibilities are used. (Scheme 27)

Scheme 27

Throttle Angle Influence On Injector Open Time

Idle is recognized by the low voltage value input from the potentiometer when the throttle is closed. This signal is adaptive to compensate for minor wear changes in the throttle plate position when closed. Part load is recognized by the varying voltage input value from the potentiometer while driving the vehicle at part throttle conditions. Full load enrichment is recognized from the high voltage value input from the potentiometer under full throttle conditions. The PCM modifies the ms injection time for all positions of the throttle. Considerations for other operating conditions such as vehicle speed, load and temperature, are also factored into the actual calculated time value.

Oxygen Sensor Signal Influence On Injector Open Time

The oxygen sensor controlled air/fuel ratio constantly cycles between lean and rich within a very narrow range (lambda window). (Scheme 28)and (Scheme 29). This cycling produces a voltage signal from 0.15 (lean) to 0.85 (rich) volts on a Bosch system or changes the voltage drop of the resistive jump oxygen sensors of the Siemens systems causing a voltage swing to occur at the monitoring circuit(s) in the control module. The voltage swings (hi to low) contain information on the amount of residual oxygen in the exhaust gas. This cycling in the oxygen sensor control circuit is caused by a "dead time" delay. The delay is from the point the fuel is metered to the point at which the exhaust gas is produced and detected at the oxygen sensor in the exhaust system. The constantly changing oxygen sensor input to the PCM is needed to correct the ms injection time to ensure that the ideal air/fuel ratio is maintained. The PCM monitors amplitude of the signal (highest voltage or range sensor is producing), switching time of the signal (how fast from lean to rich) and frequency of complete cycles (how many within a period of time). (Scheme 30)and (Scheme 31). These characteristics provide info to PCM that reflect overall condition of the sensor.

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Post Catalytic Converter Sensor Signal

The post-catalyst oxygen sensors monitor the efficiency of the catalyst as a requirement of OBD II. This signal also provides feedback of the pre-catalyst sensor efficiency and can cause the PCM to trim injection time to correct for slight deviations.

On Bosch systems, if catalyst is operating efficiently, most of the remaining oxygen is stored within the catalyst. The signal fluctuates sightly in the higher end of the voltage scale (approximately.6 volt). If the post-sensor shows excessive fluctuation (echoing the scope pattern of the pre-sensor), this indicates that the catalytic converter is not functioning correctly and cannot store the oxygen (fault set). On M5.2-M73 and all M5.2.1 systems, if the post sensor fluctuation moves out of the normal voltage window, this indicates that the pre-sensor is not performing properly due to slight deterioration. These systems trim the ms injection time to compensate for this condition.

On Siemens systems, the function of the post-catalytic converter sensor operates similarly to the Bosch system. These sensors produce a swinging signal but lean-to-rich are at opposite ends of the scale due to the sensor design. When viewing a Siemens post oxygen sensor signal on a scope, the displayed value indicates a lean or excessive oxygen quantity indicating a defective catalytic converter. This difference is due to the catalytic converter construction material and the logic of the Siemens control systems.

Oxygen Sensor Heater Relay & Heating Resistor

A temperature of about 572°F (300°C) is needed for oxygen sensor operation. In order to quickly heat sensor, a heating resistor is included in oxygen sensor.

The PCM provides a ground path for oxygen sensor heater relay, which then provides battery voltage to oxygen sensor heating resistor in oxygen sensor. The oxygen sensor heater relay is activated when ignition is on. Relay is switched off when engine reaches certain speed and load.

Idle Speed Control Valve

Idle speed is kept constant by an idle speed control valve, which supplies engine with necessary amount of air. Idle speed control takes place during period in which throttle potentiometer, or TPS, detects idle setting. The pre-programmed idle speed values in PCM are compared with actual operating values and corrected to compensate for component wear and other factors, such as minor air (vacuum) leaks.

When engine management system detects engagement of a drive range (1, 2, 3 or "D"), idle speed is increased by idle speed control valve to compensate for engine speed drop caused by engagement of torque converter. On A/C-equipped models, idle speed is also temporarily increased when A/C system is switched on. Upon receiving A/C compressor signal, quantity of air required for idle speed is corrected.

IGNITION TIMING CONTROL (STATIONARY & ROTARY SYSTEMS)

Basic triggering of the output (primary on/off) is based on inputs of engine speed and the position of crankshaft. Reference position signal (one pulse per rotation) establishes TDC position of crankshaft by PCM. Engine speed signal is then used to determine exact position of each cylinder for timing control. Ignition timing can then be updated between individual spark plug firings, as needed. This is the basis for all Bosch stationary and rotary systems.

IGNITION TIMING CONTROL (SIEMENS)

Crankshaft and camshaft position sensors are used to determine precise timing of ignition coils. If camshaft position sensor signal becomes impaired during engine operation, precise single ignition triggering continues. If signal is still impaired on next engine start, system triggers coils in double ignition to provide failsafe running. Additionally, secondary side of ignition is monitored using ignition feedback resistor. Control module measures duration of time it takes monitored voltage drop for each ignition coil to dissipate below 2 volts. Time scale constantly changes based on engine speed. If there is no feedback signal present (zero volts) there is no spark present. If 2 volt signal is not maintained long enough, control module detects this as a week spark. Primary and secondary monitoring is used in conjunction with mechanical misfire detection feature. This combination assures maximum misfire detection and prevents possible engine damage and reduced emissions with the presence of a misfire.

Ignition Timing Control & Anti-Knock Function (6-Cylinder & V8)

Ignition timing is controlled for each cylinder by means of a separate ignition coil, eliminating unnecessary high tension distributor. This ignition system is referred to by manufacturer as a coil ignition system with static high tension distribution.

For each cylinder, an output stage-controlled ignition coil is provided, which routes secondary voltage (up to 32,000 volts) via spark plug connector to spark plug. This configuration permits independent control of ignition timing.

By eliminating distributor, effective range of ignition timing control is increased by about 10 degrees, to a maximum of 59 degrees per cylinder. A camshaft sensor is used to maintain correct firing order. Ignition timing is retarded (anti-knock function), depending on inputs from knock sensors, in order to prevent pre-ignition of air/fuel mixture in combustion chamber.

Catalytic Converter Protection Function

If malfunctions on primary side of ignition system are detected by PCM, fuel injector(s) for that cylinder(s) will be turned off. This effectively prevents rich exhaust gas mixtures from reaching catalytic converter.

LEAK DIAGNOSIS TEST PRECONDITIONS (X5)

The DME only initiates a leak diagnosis test every second time the criteria are met. The criteria is as follows

1. Engine off with ignition off.
2. Engine Control Module still in active state or what is known as "follow up mode" (main relay energized, control module and DME components online for extended period after key off).
3. Prior to engine/ignition switch off condition, vehicle must have been driven for a minimum of 20 minutes.
4. Prior to minimum 20 minute drive, the vehicle must have been off for a minimum of 5 hours.
5. Fuel tank capacity must be between 15 and 85 percent (safe approximation between 1/4 -3/4 of a tank).
6. Ambient air temperature between 20-95°F (-70-35°C).
7. Altitude less than 8,202 feet.
8. Battery voltage between 11.5 and 14.5 volts. When these criteria are satisfied every second time, the PCM will start the fuel system leak diagnosis test. Test will typically be carried out once a day.

DIAGNOSIS MODULE - TANK LEAKAGE (M5 & X5)

A Fuel System Leak Diagnosis Pump (LDP) is equipped on the M5 and X5. The pump will eventually replace the current vacuum LDP on all vehicles. The pump is manufactured by Bosch to BMW specifications. Bosch PCMs identify the electrical function of the pump as DM-TL. Siemens PCMs identify the electrical function of the pump as LDP-M1. The pump is located in the driver's side rear wheel well. (Scheme 32)

Scheme 32

Function

In its inactive state, filtered fresh air enters the evaporative system through the sprung open valve of the pump. When the DME activates the pump for leak testing, it first activates only the pump motor. This pumps air through a restrictor orifice (1.0 or 0.5 mm) which causes the electric motor to draw a specific amperage value. This value is equivalent to the size of the restricted. The solenoid valve is then energized which seals the EVAP system and directs the pump output to pressurize the EVAP system. (Scheme 33) The EVAP system is detected as having a large leak if the amperage value is not realized, a small leak if the same reference amperage is realized or no leak if the amperage value is higher than the reference amperage. The DC Motor LDP ensures accurate fuel system leak detection for leaks as small as.020" (.5 mm). The pump contains an integral DC motor which is activated directly by the engine control module. The PCM monitors the pump motor operating current as the measurement for detecting leaks. The pump also contains an PCM 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 breathe through the inlet filter similar to full down stroke of current vacuum operated LDP. (Scheme 34)

Scheme 33

Scheme 34

DC Motor LDP Inactive - Normal Purge Valve Operation

In its inactive state the pump motor and the change over valve of DC Motor LDP are not energized. When purge valve operation occurs filtered air enters the fuel system compensating for engine vacuum drawing on the hydrocarbon vapors stored in the charcoal canister.

LEAKAGE DIAGNOSIS PUMP (LDP)

LDP system is capable of detecting a leak as small as.019" (0.5 mm). LDP is a unitized component that contains vacuum chamber, pneumatic pump chamber, DME activated vacuum solenoid, and reed switch providing a switched voltage feedback signal to DME. LDP assembly is only replaceable as a complete unitized component, however, it is separate from charcoal canister.

During every engine cold start, LDP solenoid is energized by the PCM. Engine manifold vacuum enters upper chamber of LDP to lift up spring loaded diaphragm pulling ambient air through the filter and into the lower chamber of the LDP through one way valve. Solenoid is then de-energized, spring pressure closes the vacuum port blocking the engine vacuum and simultaneously opens the vent port to balance tube which releases captive vacuum in upper chamber. This allows compressed spring to push the diaphragm down, starting limited down stroke. (Scheme 35)

The air that was drawn into the lower chamber of the LDP during the upstroke is forced out of the lower chamber and into the evaporative system. Electrically controlled repetitive up/down stroke is cycled repeatedly building up a total pressure of approximately +25mb in the evaporative system. After sufficient pressure has built up (LDP and its cycling is calibrated to the vehicle), leak diagnosis begins and lasts about 100 seconds. Upper chamber contains an integrated reed switch that produces a switched high-low voltage signal that is monitored by the PCM. Switch is opened by magnetic interruption of the metal rod connected to the diaphragm when diaphragm is in top dead center position. Repetitive up/down stroke is confirmation to the PCM that valve is functioning.

PCM also monitors the length of time it takes for the reed switch to open, which is opposed by pressure under the diaphragm in the lower chamber. The LDP is still cycled, but at a frequency that depends upon the rate of pressure loss in the lower chamber. If pumping frequency is below parameters, there is no leak present. If pumping frequency is above parameters, this indicates sufficient pressure can not build up in lower chamber and evaporative system, indicating a leak. A fault code can be recorded by each PCM indicating an evaporative system leak. After test completion, PCM releases ground path to LDP and internal spring pushes diaphragm for full down stroke. At bottom dead center, diaphragm rod opens canister vent valve. This allows for fresh air intake from filter for normal purge system operation. The LDP is diagnosable with DIS including a service function activation test.

Scheme 35

EVAPORATIVE SYSTEMS MONITORING (LDP SYSTEM)

Comparing temperature signals and correcting for lowest possible temperature value provides safeguards against setting faults and ultimately an erroneous MIL activation. The following scenarios provide insight into how system can provide guaranteed test results.

CAN bus ambient temperature signal is within range and a leak is detected during the leak test. After the conditions are met for comparing the CAN bus signal with the intake air temperature sensor signal which is detected as out of range, test is ended with no fault stored; or within range, fault stored. The ambient temperature is out of range at the time of engine start, this leads to a temporary end of test, the leak test is carried out as soon as all conditions are OK for an accurate test result. Only when the ambient temperature is within specified range and no leak is detected during the leak test is the system considered to be leak free.

FUEL TANK

Fuel tanks are made either of steel or high density polyethylene depending on the vehicle. All vehicle fuel tanks contain internal fuel pump(s). Saddle type fuel tank provides a tunnel for the driveshaft but creates 2 separate low spots in the tank. A siphon jet is required with this type of tank to transfer fuel from the left hand side, linked to the fuel return line. As fuel moves through the return, the siphon jet creates a low pressure (suction) to pick up fuel from the left hand side of the tank an transfer it to the right hand side at the fuel pick up.

Fuel vapors are routed to engine via an activated carbon canister. Installed between carbon canister and air manifold is a purge control valve. Valve restricts flow of air based on sensor inputs to PCM.

Electrical activation of purge control valve depends on engine speed and load. Vacuum line to intake manifold is closed as long as valve is supplied with voltage. When no power is applied to valve, it can be opened by vacuum in intake manifold.

The fuel evaporation control cycle begins as soon as oxygen control system is active (closed loop mode). Upon completion of purge cycle, valve is closed for about 30 seconds. When engine is shut off, valve remains closed for another 3 seconds to prevent engine run-on.

SELF-DIAGNOSTIC FEATURE

PCM has a self-diagnostic feature which detects malfunctions in emission-related components and stores Diagnostic Trouble Codes (DTCs). PCM provides a substitute value if a failure occurs in engine (coolant) temperature sensor, intake air temperature sensor, airflow meter or exhaust gas oxygen sensor. These substitute values are canceled when normal engine operation is resumed. To aid in trouble shooting, stored fault codes and sensor values can be monitored via PCM and actuated components.

Vehicles are equipped with an OBD-II self-diagnostic system which can utilize a generic scan tool connected to in-vehicle Data Link Connector (DLC). In addition, vehicles are also equipped with a BMW self-diagnostic system which accesses DTCs using special BMW hardware and software connected to underhood BMW engine diagnostic connector socket. See SELF-DIAGNOSTICS article.

An emission-related component or circuit failure will activate MIL on instrument cluster.

MISCELLANEOUS CONTROLS

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if they malfunction.

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 PCM. 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 No. 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 No. 5. The resonance wave, along with the intake velocity, enhances cylinder filling. The PCM 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. When the engine speed is greater than 4100 RPM (which varies slightly - temperature influenced), the solenoid is de-energized. The resonance flap is sprung open, allowing flow through both resonance tubes, increasing volume.

IDLE SPEED CONTROL

The PCM determines idle speed by controlling an idle speed actuator (dual winding rotary actuator). The basic functions of the idle speed control are

1. Control the initial air quantity (at air temperatures less than 32° F (0° C), the MDK is simultaneously opened)
2. Variable preset idle based on load and inputs
3. Monitor RPM feedback for each preset position
4. Lower RPM range intake air flow (even while driving)
5. Vacuum limitation
6. Smooth out the transition from acceleration to deceleration Idle speeds will vary (idle speed stabilization)
7. During the warm up phase
8. When Air conditioning is activated
9. When a drive gear is selected
10. When heating the passenger compartment
11. At all electric fan speeds

If nominal RPM is modified (idle speed increase) by DIS service function (if applicable) Emergency Operation of Idle Speed Actuator: If a fault is detected with the idle speed actuator, the PCM 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 MDK 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.

INTAKE AIRFLOW CONTROL

Under certain engine parameters, the MDK throttle control and the idle speed actuator (ZWD) are operated simultaneously. The PCM detects the driver's wish from the twin potentiometers monitoring the cable/pulley position. This value is added to the idle speed control value and the total is what the PCM uses for MDK activation. The PCM then controls the idle speed actuator to satisfy the idle air fill. In addition, the MDK will also be activated (pre-control idle air charge). These functions are utilized to maintain idle RPM. The MDK is electrically held at the idle speed position, and all of the intake air is drawn through the idle speed actuator. Without a load placed on the engine (less than 15 percent load), the MDK will not open until the extreme upper RPM range. If the engine is under load (greater than 15 percent), the idle speed actuator is open and the MDK will also open. In the upper PWG range (approximately greater than 60 percent), the MDK is switched off. The throttle valve is opened wider exclusively by the pulley via the spring linkage. At the full throttle position, kickdown is obtained by depressing the accelerator pedal fully. This will overwind the pulley, but the spring linkage will not move the throttle plate past 90 degrees of rotation. If the MDK is defective, it is replaced as a unit and is not internally serviceable.

VARIABLE VALVE TIMING SYSTEM (VANOS)

Valve timing is changed on both the intake and the exhaust camshafts. This system, referred to as double VANOS, provides 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, and reduction in fuel consumption.

Double VANOS consists of 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, and 2 camshaft position sensors (Hall effect). Initial timing is set by gear positioning and the chain tensioner. Hydraulically controlled actuators move the helical geared cups to regulate camshaft timing. 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 cases camshafts to advance or retard. Adjustment rate is dependent on oil temperature, oil pressure, and engine RPM.

With extremely hot oil temperatures, VANOS is deactivated. If the oil is too thick (wrong viscosity) a fault could be set. When the engine is started, the camshafts are in failsafe position (deactivated). Intake camshaft is in retarded position, held by oil pressure from sprung open solenoid. Exhaust camshaft is in advanced position, held by a preload spring in actuator and oil pressure from sprung open solenoid. After 50 RPM (2-5 seconds) from engine start, PCM is monitoring exact camshaft position. PCM 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 temperature. Double VANOS system is fully variable. When the PCM 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. (Scheme 36)

On V8 engine, there is an inlet and exhaust solenoid for each camshaft. These solenoids are both installed on one side of the control piston. The engine control module regulates the solenoids through a pulse width modulated signal to apply or drain control oil pressure from the VANOS pistons. Camshaft adjustment is based on several characteristic maps stored in the control module. The main control parameters for camshaft adjustment are derived from the engine speed signal and the throttle valve position signal

Scheme 36

See also:
• WIRING DIAGRAMS
• BMW MODIC DIAGNOSTIC TESTER
• ENGINE MANAGEMENT SYSTEM
• INPUT DEVICES (MOTRONIC)
• INPUT DEVICES (SIEMENS)
• OUTPUT SIGNALS (MOTRONIC)
• OUTPUT SIGNALS (SIEMENS)