Table of Contents X5 Updates Subject Page EHC2 . 3 Purpose of the System . 3 History . 3 System Components . 4 Air Supply Unit . 4 Pressure Accumulator . 6 Ride Height Sensors . 8 Air Suspension . 9 Control Unit . 9 Switch Assembly .10 Principle of Operation . 11 Control Modes.13 4.6is . 17 Engine. 17 Transmission .18 Brakes. 18 Additional Standard Features .19 Review Questions .20 Initial Print Date:3/02 Revision Date: X5 Updates Model: X5, X5 4.6 iS Production: 9/02 Objectives: After completing this module you should be able to: • Recognize the components of EHC2 • Locate the EHC2 components • Understand the operation and diagnose EHC2 • Recognize the X5 4.6iS • Relate the additions and modification to the 4.6iS 2 X5 Updates Two Axle Air Suspension Purpose of the System The two axle air suspension system (EHC2) offers advantages over the single-axle air sus¬ pension with respect to ride comfort and off-road capability. Lowering the entire body makes it easier to enter, exit, load and unload the vehicle. The vehicle's off-road capability was improved by providing the possibility for increasing the ground clearance of the body. The driver can now choose between three different ride levels which can be set with a rock¬ er switch, as required. Automatic ride-height control for payload compensation and automatic inclination compensation continue to be fitted. Deficits of the old system The automatic payload compensation facility for the single-axle air suspension did not per¬ mit driver control. The driver could not actively control the system to make it easier to enter and exit or load the vehicle. Ride level was compensated via the rear axle only. Advantages of the new system The new system allows the ride-height control system to be controlled actively by the dri¬ ver. The twin axle air suspension allows both axles to be lowered evenly and in parallel. As a result, it is easier for the occupants to enter, exit, load and unload the vehicle. History BMW previously supplied ride-height control systems as both optional equipment and, in part, as standard equipment on the 7 Series - E23/E32(not in the US market), 6 Series - E24 (L6/M6) and 5 Series - E28 (M5). On the E39, the load of the complete rear axle was born for the first time by air suspension in combination with the optional ride height control system. The system was controlled automatically under all operation conditions, and there was no possibility for driver intervention on the X5, the rear axle previously had single axle air suspension only. The air supply unit and the control unit were adopted from the E39. The air springs were adapted to the X5. There is a standard version and a sports version. The ride-height control system (EHC) was supplied as standard in combination with the M62 engine and is available as an optional extra in combination with the M54 engine. EHC2 is optional on both the M62 and M54 versions of the X5 and not available on the 4.6isX5. 3 X5 Updates System components The X5 Two Axle Air Suspension System (EHC2) utilizes the air supply unit from EHC mounted in the luggage compartment, with the following components added or modified: • Air Supply Unit (with redesigned compressor and drier) • Pressure Accumulator • Valve Unit • Ride Height Sensor • Air Suspension Strut • Control Unit • Switch Assembly Pneumatic System of EHC2 1. Air Supply Unit 2. Rear Axle Air Bellows 3. Ride Height Sensors 4. Pressure Accumulator/ Valve Unit 5. Front Axle Air Bellows 6. Control Unit Air Supply Unit As on vehicles with single axle air suspension, the air supply unit is located in the luggage compartment under the spare wheel. As with the single axle air suspension, the auxiliary tanks for the rear air spring bellows are located in the luggage compartment. The air supply unit is configured similarly to the single axle air supply unit for the ride-height control system of the E39, which is currently in production. The functions are implemented by activating a compressor and various valves in the air supply unit and on the air accumulator valve unit. The maximum pressure of the air supply unit is 21 bar. 4 X5 Updates 6 1 2 6 3 1. Pneumatic Drain Valve 2. Electric Pilot Control Valve 3. High Pressure Vent Valve 4. Air Drier 5. Compressor 6. Sintered filter 7. To Pressure AccumulatorA/alve Unit NW Size of opening/tubing in mm. Air Supply Unit Pneumatic Drain Valve The Pneumatic Drain Valve is activated pneumatically by pressure from the control valve. This causes the drain valve to open allowing the pressure supply line to vent to atmosphere. This design allows for large air volumes to be discharged quickly and eliminates the need for a solenoid valve with high current consumption. The 21 bar pressure limiting valve is integrated in the drain valve. Electric Pressure Relief Valve The electrically activated pressure relief valve controls normal system pressure. The con¬ trol valve performs this function in conjunction with the drain valve. High Pressure Vent Valve The High Pressure Vent Valve serves as a comfort valve and is used to release system pres¬ sure after the accumulator has closed and the compressor is still running. When the high pressure vent valve has opened the compressor can be stopped quietly. Air Drier In the air drier, the air which is drawn in passes over a water absorptive filter material in the form of filter nodules which extract moisture from the air. As long as the air contains more moisture than the filter material, the individual nodules absorb and accumulate the mois¬ ture. When the air flows back, it is drier than the filter material, with the result that the air is re-humidified and the moisture is discharged into the open air. The maximum water storage capacity of the filter is 30 g. 5 X5 Updates Compressor with Drier Top: Air Drying Bottom: Dissipation of water to air Compressor Compressor operation is the same as in EHC with the following technical improvements: • Addition of a temperature sensor (Located on the compressor cylinder head) Temperature sensor switches off the compressor at temperatures above 110°C. • Extended compressor ON time (180 seconds) • Redesigned air drier to compensate for additional air volume. Pressure Accumulator The twin axle air suspension system now features a pressure accumulator which forms an air accumulator valve unit in combination with the valve. The air accumulator valve unit is located beneath the vehicle floorpan in the right-hand sill area. 6 X5 Updates i Pressure Accumulator Unit which includes: Pressure Accumulator Pressure Sensor Valve Unit Front The pressure accumulator decreases the load on the compressor and significantly reduces the time required for large changes in ride height. The EHC 2 control module monitors system pressure via a pressure sensor mounted on the accumulator. Normal system pressure is 15.7 +/- 0.7 bar. Minimum system pressure is 9 bar. The pressure accumulator's charge is sufficient to fill the four suspension struts once from the Access position to the normal position and compensate for vehicle load up to maximum gross weight. i Accumulator/Valve Unit 1. Air Lines Yellow-Black Front Red-Blue Rear 2. Pressure Accumulator 3. Connecting Cable 4. Pressure Sensor 5. Valve Unit 1 2 1 Valve Unit 1. Connections for Air Lines 2. Pressure Accumulator valve Valve Unit In the valve unit, four bellows valves and the pressure accumulator valve are activated. The bellows valves and the pressure accumulator valve are solenoid valves which are closed under spring pressure when de-energized. Pneumatic Layout of Control Valve 1. Pressure Accumulator 2. Accumulator Pressure Sensor 3. Pressure Accumulator Valve 4. Bellows Valves 5. From the Air Supply Unit NW Size of opening/tubing size in mm. 7 X5 Updates Ride Height Sensor The control unit obtains information about the ride height of the vehicle via a ride height sen¬ sor attached to each of the four wheels. 60° Rear Axle Ride Height Sensor The ride height sensor is an angle Hall sensor which is activated by a ring magnet. The ring magnet is polarized vertically from north to south. The magnetic field line of the ring magnets intersect a Hall cell. The Hall cell is arranged in such a way that only the horizontal components of the field lines are evaluated. This results in different field line strengths at different positions of the ring magnet. The Hall cell mea¬ sures the field strength of the magnetic flux and converts it into an analog signal with a volt¬ age level between 0.5 and 4.5 V. 1 stx ( !i! I) "\JLS Sensor Principle of Operation 1. Ring Magnet 2. Hall Cell 3. Longitudinal magnetic field lines, low voltage 0.5V 4. Transverse magnetic field lines, high voltage 4.5V 8 X5 Updates Air Suspension Strut Rear Minor modifications were made to the rear axle air springs. The air springs and the dampers are configured separately at the rear axle. Front The air suspension replaces the steel suspension at the front axle, i.e. the spring bellows is attached to the damper. The front air suspension strut and the impact absorber form a complete unit. Air Suspension Strut 1. Auxiliary Spring 2. Air Bellows 3. Damper Control Unit The EHC2 Control Unit is located behind the glovebox adjacent to the General Module. The connector is a black 54 pin connector. Inputs received directly into the control unit are: Ride Height Level Sensor (X4) Up and Down requests from the switch assy. General Module (Load cutout signal) CAN Bus Inputs K Bus Inputs Pressure Sensor Compressor Temperature Outputs include: Air Unit Control (Activation) Front and Rear Axle Valves LED’s for Switch Unit Compressor Relay Pressure Accumulator 9 X5 Updates Switch Assembly The dash mounted switch assembly supplies a momentary switched ground to the EHC2 Control Unit requesting a ride height change in the up or down direction. Three LED’s pro¬ vide current ride level selected and target ride level if a request for change has been made. The LED for the current ride height will always be illuminated. The LED for the target ride level will flash until the new ride level is reached. Notes: 10 X5 Updates Principle of Operation Ride Height Control Operations In addition to the automatic ride-height control system for payload compensation, the dri¬ ver can set three different vehicle ride heights. • Off-road (+25 mm), high ground clearance to a max. speed of 50 km/h • Standard (0 mm), normal ride level • Access (-35 mm), for entry and exit, loading and unloading to a max. speed of 35 km/h or can be activated in Standard mode at road speeds < 25 km/h The various heights are selected by scroll rocker. Light emitting diodes indicate the present ride height setting. Ride height can be adjusted from terminal 15 and with the doors closed. The hood and tail¬ gate may be open. The system also controls inclination automatically, like the single axle air suspension. All control operations are executed without stopping at intermediate levels. The vehicle is configured pneumatically in such a way that the front and rear axles can be lowered in par¬ allel in any load situation. Depending on the load situation, either the front axle or the rear axle is slightly quicker. On account of the different control speeds, a difference in height between the two axles is possible during all control operations. If a max. permissible thresh¬ old is exceeded, the quicker axle is stopped briefly. The various levels can be preselected while travelling. Changeover between ride levels is effected at the speed threshold values defined in the control unit. The control unit monitors the change-over. As soon as the driver sets a new target ride level by pressing a button or when a change¬ over is initiated automatically by a specific driving condition, the LED for the current ride level remains lit and the LED for the target ride level begins to flash. When the new level is reached, the LED for the previous level goes out and the LED for the new level reached stays lit permanently. 11 X5 Updates Down button or >50km/h Off-Road (+25 mm) Down Button and <80km/h and Accumulator pressure threshold and/or compressor temperature threshold Standard (0 mm) Access (-35 mm) <25km/h Up button and <50km/h Up button or >35km/h The various levels can be preselected while travelling. Changeover between ride levels is effected at the speed threshold values defined in the control unit. The control unit monitors the change-over. As soon as the driver sets a new target ride level by pressing a button or when a change¬ over is initiated automatically by a specific driving condition, the LED for the current ride level remains lit and the LED for the target ride level begins to flash. When the new level is reached, the LED for the previous level goes out and the LED for the new level reached stays lit permanently. If a ride level selection is not allowed, the LED indicating the momentary ride level of the vehicle flashes for 3 seconds. A special case is preselection of Access levels while travelling. The Access LED flashes and the LED for the original ride level is lit permanently. However, this does not mean that a con¬ trol operation has already begun. The control operation does not actually begin until the speed threshold which the Access level allows is reached or undershot. 12 X5 Updates In addition to the LED indicator, the following text messages can be displayed in the instrument cluster: • TRAILER MODE A coupled trailer is identified via the trailer connector. To avoid damaging the trailer and the vehicle, changes of vehicle level are generally avoided. The standard level is "frozen." If the trailer is coupled at a level other than the Standard level, the vehicle ride level is not changed to Standard unless a button is pressed or the speed threshold for auto¬ matic change-over is reached. The standard level is then "frozen" until the trailer con¬ nector is disconnected. • RIDE HEIGHT CONTROL INACTIVE Faults in the system and on the control unit which are only identified by the instrument cluster, e.g. control unit disconnected • RIDE HEIGHT CONTROL INACTIVE + MAX. 60 km/h For safety-critical faults (vehicle is too high or at inclination) Control Modes Sleep mode If the vehicle is parked, it enters Sleep mode after 16 minutes. No further control opera¬ tions are executed. A "watch dog" wakes up the control unit for a few minutes every 6 hours (wakeup mode) in order to compensate for possible inclination of the vehicle. (Vehicle height may only be corrected once as air supply unit only operates with engine running.) Wake-up In wake-up mode, the control unit is woken up for a set period of time in order to com¬ pensate for possible inclination of the vehicle. Inclination of the vehicle can be caused by large temperature differences or by minor leaks. Adjustments to the front and rear axles ensure that the vehicle is visually level. To minimize power consumption, the vehicle is low¬ ered only. The nominal level of the lowest wheel serves as the nominal level for all other wheels. The lowest nominal level to which the vehicle is lowered is the Access level (-35 mm). Exception: if the vehicle is parked at Access level, the vehicle is lowered to max. -50 mm in wake-up mode. If the vehicle is parked for a prolonged period of time and there is a leak in the system, further loss of pressure does not produce a change of ride level since the weight of the body is born by the auxiliary suspension and the residual tire pressure. Advance /Overrun When the vehicle is woken out of sleep mode by the load-cutout signal (VA), it normally enters advance / overrun mode. Since the engine is not (no longer) running in this mode, however, there are restrictions on the control operations that can be performed in order to conserve the battery. Ride level compensation is restricted to tolerance ranges of 20 mm and 25 mm in the up and down directions respectively. This serves to reduce the frequen¬ cy of control operations. 13 X5 Updates All control operations in advance / overrun mode are executed as long as pressure is avail¬ able in the accumulator. When the accumulator is empty and the engine is turned off, con¬ trol operations are directly driven by the compressor. User-activated changes of ride level and filling of the accumulator are not possible. Terminal 15 As soon as the ignition is turned on (terminal 15), the user is allowed to lower the ride level as required. However, it is still not possible to raise the ride level or fill the accumulator. Ride level is compensated outside a narrow tolerance range of 10 mm upwards and 10 mm downwards. Engine "on" Ride level compensation, raising and lowering the vehicle's ride height as well as filling the accumulator are permitted when the engine is running. The compressor also starts up dur¬ ing every control operation. Ride level is still compensated outside the narrow tolerance range of +10 mm. As long as the vehicle is stationary, high speed filtered ride level signals are used to detect a change of load. This allows the system to react immediately to changes in ride level. As soon as the vehicle is travelling, it changes over to low speed filtered ride-level signals. The system no longer reacts to bump movements caused by road surface unevenness. A mean value is formed over a prolonged period of time, i.e. payload is only altered by the progressive emptying of the fuel tank. The high speed filter is not used until the vehicle is stationary again and a lid is opened. If no lid is opened, the vehicle logically cannot be loaded or unloaded. Power Down 14 X5 Updates Workshop Hints If a threshold level is exceeded on all 4 wheels when the vehicle is stationary, the control unit assumes that the vehicle has been raised on a workshop platform. There are three possible reset conditions for workshop platform recognition: • The original level values are undershot at all four wheels, • A selection is made by button, • A speed of >40 km/h is recognized for 3 s. Vehicle jack If the lowering speed at a wheel is too low during the lowering operation, the system assumes that the wheel is jacked up. However, the downward velocity must be less than a certain preprogrammed speed threshold. If the system detects a jacked wheel, it stores the height of this wheel. Car jack recognition is reset when the stored ride height is again undershot. When a trav¬ elling speed of 40 km/h is maintained for at least 3 s, another control attempt is performed. The carjack recognition can also be reset by button selection. Please note that the system also controls ride height in diagnostic mode. For this reason, Belt Mode must be activated before carrying out work on the system or before setting the vehicle ride height. Belt Mode: Heights are fixed and are not compensated. If Belt Mode is set, the function LED is off. The text message "ride-height control system inactive" appears in the instrument cluster. Transport Mode: The Transport Mode setting is for transportation purposes. When the ignition is turned on, the message "ride-height control system inactive" appears. Heights are increased or decreased depending on ignition key status, e.g. ride height is reduced when the vehicle is lashed to a ship or train and raised when the "Engine on" signal is generated and when the vehicle is transported on a transporter truck. The correct ride height is set to ± 5 mm via "Activate components." The left and right ride levels are set separately at the rear axle. The ride levels are then set at the front axle. The left and right air springs are adjusted jointly for this purpose. Following this, the new ride height for the front and rear axles is stored via the "Offset func¬ tion." Before replacing components, the system must be depressurized! This is done in the diag¬ nostics via "control unit functions," "Component activation," "Pressure-relieve front axle/rear axle." Repeat the activation procedure 6 times. 15 X5 Updates If the fabric of the bellows is visible, then the bellows must be replaced. Upon completion of repair work, the air suspension system of the vehicle raised on the workshop platform must be refilled with air via the diagnostics. The activation procedures must also be repeated 6 times. This prevents the bellows from being folded incorrectly. The vehicle must with be set down on its wheels when the suspension struts are depres¬ surized! Important Workshop Hint Similarly, a defective vehicle with leaky pneumatic system must not be raised on the work¬ shop platform. If depressurized, the bellows would contract under suction forming incorrect folds. These folds could result in malfunctions later on. Areas on the air bellows which can possibly become leaky are the O-ring at the piston rod and the seal carrier on the roll piston. The connectors attached to all cables are identical to the connections on the single-axle air suspension. 6 mm cable is used. The tightening torque is 3±1 Nm throughout the system. Special care must be taken when handling breakage-prone plastic parts of air suspension elements. Upon completion of repair work, Belt mode must be deactivated via the diagnostics. The function LED on the button comes on. No text message appears in the instrument cluster. The system is OK and ready for operation. 16 X5 Updates X5 4.6 iS The X5 4.6iS is an additional model added to the X5 family of SAV’s. The 4.6 receives model code FB93/0266 and is available start of production 10/01. Features added to the 4.6 versus the 4.4: • Increased Engine Displacement/Florsepower • Increased Transmission Capacity • Upgraded Brakes • Additional Standard Features • Special/Limited Exterior Colors • New Interior Textures Engine The engine for X5 4.6iS is a M62 with increased displacement and horsepower. M62 4.6 M62 4.4 Displacement (cm 3 ) 4619 4398 Bore (mm) 93.0 92.0 Stroke (mm) 85.0 82.7 Compression Ratio 10.5:1 10.0:1 Maximum Florsepower@RPM 340 @ 5700 290 @ 5400 Maximum Torque (NM)@RPM 475 @ 3700 440 @ 3600 Engine Management System ME7.2 ME7.2 Emission Compliancy LEV LEV Performance 0-60 mph 6.2 Seconds 7.4 Seconds Diagnostics of the 4.6iS are carried out in the same manner as the X5 4.4. Transmission The X5 4.6iS is available only with a ZF A5S 440Z 5-speed automatic transmission which features modified internal components. Many internal components, including the torque convertor have been modified to handle the increased torque and horsepower. The transmission is specific to the X5 4.6iS and no other transmission should be substitut¬ ed. Programming of the transmission is also changed to better accommodate the vehicle. Transmission management will be by EGS 8.60.2. Transmission diagnostics will be handled in the same manner as other models. Brakes Front and rear brakes are upgraded on the X5 4.6iS. Brake rotor size is increased from the 13.1 in. front normally found on the X5 4.4 to a size of 14.0 in. on the 4.6iS. While rear brake rotor diameter remains the same on the 4.6iS at 12.8 in., the thickness of the rotor is increased and the rear rotor is now ventilated similar to the front rotor. With these changes brake calipers, brake rotors and brake pads for both front and rear are vehicle specific for the X5 4.6 and similar components from other models may not be inter¬ changed. X5 Updates Additional Standard Features The following equipment is added to the 4.4 model equipment for the X5 4.6iS: Glass Moonroof Roller Sun Blinds For Rear Doors Self Dimming Mirrors Rear Seat Back Adjustment Rear Seat Heating PDC Rain Sensor Premium Sound System CD Changer Privacy Glass Colors Special colors and combinations along with special interior packages are available. Refer to marketing information for current availabilities. 19 X5 Updates Review Questions 1. List the advantages of the EHC2 over EHC as used in the X5. 2. What component is responsible for limiting the maximum pressure in the EHC2? And what is the maximum pressure/minimum pressure? 3. Why is a pressure accumulator used? 4. The control unit for EHC2 is located ? 5. List the possible ride heights possible with EHC2. 6. If the driver fails to return the system to the standard position what happens as the X5 goes down the road. 7. What causes the control unit to assume the vehicle is being raised on a platform in the workshop?_ 8. Why is it important not to raise a vehicle with a leaky pneumatic system? 9. How do the front and rear brakes of the 4.6 is compare with the 4.4. 10. Is it possible to interchange transmissions from a 4.6 to a 4.4? 20 X5 Updates