Page 2 - Model: Level Control Systems; After completion of this module you should be able to:
2 Level Control Systems Model: Level Control Systems Production: E32 750iL 88-94 (Hydro-Pneumatic) E32 740iL 93-94E38 750iL 95-01E38 740iL 95-01E34 Touring 525iT, 530iTE39 Touring 528iT, 540iT, 525iT (EHC I)E53 X53.0i, X5 4.4i and X5 4.6is (EHC I)E53 X5 3.0i, X5 4.4i (EHCII)E66 745Li, 760Li from 03 ...
Page 3 - Purpose of the System
3 Level Control Systems Level Control Systems Purpose of the System The primary function of Level Control Systems is to maintain the height of the vehicle asclosely as possible to a predetermined level under all load conditions. This constant level allows the suspension system to maintain the alignm...
Page 4 - Hydropneumatic Rear Leveling System; The system is installed on:
4 Level Control Systems Hydropneumatic Rear Leveling System This module pertains to the hydropneumatic rear suspension system with the engine dri-ven piston pump. The earlier system using the electro-hydraulic pump will not be dis-cussed. The self-leveling suspension system is designed to maintain v...
Page 5 - System Components; Component Layout E32
5 Level Control Systems System Components The system consists of the following components: • Tandem Hydraulic Pump • Oil Reservoir • Pressure Reservoir (2) • Control Valve with Regulating Linkage • Camber Warning Switch (E32 and E34) • Rear Shock with LAD Module • Expansion Hose, Pressure Lines and ...
Page 6 - Tandem Pump
6 Level Control Systems Tandem Pump The tandem pump consists of a vane pump for power steering and a radial pump for self-leveling suspension. Both pumps are driven by the same shaft and have separate oil feedsfor each system. The radial pump has the capacity to pump 102 liters of oil per minute. Th...
Page 7 - Oil Reservoir; Pentosin CHF 11S
7 Level Control Systems Oil Reservoir The single reservoir stores fluid for both the self-leveling and power steering systems.Incorporated in the reservoir, is a reed type level warning switch. If the fluid level drops andthe contact closes, a signal is sent to the check control module and a warning...
Page 8 - Pressure Reservoirs; Gas Chamber
8 Level Control Systems Pressure Reservoirs The oil pressure reservoirs (2) on each strut incorporate a membrane and are nitrogen gasfilled. They are designed to absorb the oil which is expelled from the struts during down-ward movement, the gas in the reservoirs is compressed and pushes the oil bac...
Page 9 - Control Valve; • Raise
9 Level Control Systems Control Valve The rotary control valve located on the rear suspension has three positions: • Raise • Level • Lower The control lever is attached to the rear stabilizer bar to sense vehicle loading. When thevehicle is loaded (passenger or luggage) the suspension drops and the ...
Page 10 - Rear Shocks; LAD Housing
10 Level Control Systems Rear Shocks With Load Dependent Module (LAD) E32/E34 Rear Shockwith LAD E38 Rear Shock with LAD PressureReservoir Connection LAD Housing ValveHousing ControlPiston Pressure Reservoir Connection LAD Housing
Page 11 - LAD Module
11 Level Control Systems LAD Module With a high pressure applied to the control piston,the flow resistance is high and the damping forcewill be stiff. The load dependent module is a control valvethat regulates the flow of oil between the strutand the pressure reservoir. The control piston in the (LA...
Page 12 - Camber Warning Switch (E32 AND E34 Touring)
12 Level Control Systems Camber Warning Switch (E32 AND E34 Touring) The self-leveling suspension systems used in the E32 and the E34 Touring are equippedwith a camber warning switch. The switch is mounted on the right rear axle support andconnected through a rod to the semi-trailing arm. The functi...
Page 14 - EHC System Overview
14 Level Control Systems EHC System Overview EHC I Single Axle Air Suspension E39/E53 EHC II Dual Axle Air Suspension E53 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
Page 15 - Control Module
15 Level Control Systems Single Axle EHC I System Components (E39/E53) The EHC system consists of the following components: • EHC Control Module • Air Springs (2) with Air Reservoirs • Rear Axle Level Sensors • Encapsulated Air Supply (LVA) • Warning Indicator Control Module The Control Module is mo...
Page 17 - Air Springs; A warning lamp indicator is illuminated used on the basic cluster.
17 Level Control Systems Air Springs The air spring is made from a flexible rubber material. Itforms an air tight cavity which provides the calculatedspring rate required for the sport wagon. As the spring compresses downward the bottom edgeof the rubber material rolls along the vertical surface oft...
Page 18 - The air supply system consists of the following components:
18 Level Control Systems Air Supply System (LVA) The air supply system is identified as the LVA in the diagnosis program and in the repairmanual. It is mounted in the spare tire well compartment. The components are housed ina sound deadening carrier, through rubber bushings, to prevent operating noi...
Page 19 - LVA Location X5
19 Level Control Systems Air Supply System (LVA) Operation The single stage piston compressor produces a maximum pressure of 13.5 Bar. The com-pressor is maintenance free - provided it is used in a dust free environment. This includesthe compressor’s intake air filter. The compressor is driven by a ...
Page 21 - EHC System Operation; Normal Mode; - Transport mode is set at the factory and raises the vehicle 30mm to
21 Level Control Systems EHC System Operation A fully functional EHC system is controlled by one of three different modes of operation.The operation mode is selected by the control module based on current conditions provid-ed by the monitored input signals. The main modes of operation are: • Pre-Run...
Page 22 - Normal Mode Operation
22 Level Control Systems Normal Mode Operation Once the rear lid is closed, KL 15 switched ON and the engine started, the system switch-es into the normal operation mode. In the normal mode, the control module will constantlymonitor the input signals from the ride height sensors and will activate a ...
Page 23 - Special Operating Modes; Transport Mode; Control Interrupts; Cornering
23 Level Control Systems Special Operating Modes • Assembly Line Mode (New control module) The assembly line mode refers to control module manufacturing. New control modulesare stored in a deactivated state. The control programming is not active and must firstbe ZCS encoded. After installing a repla...
Page 24 - EHC Service Information
24 Level Control Systems EHC Service Information Diagnosis/Coding • The EHC control module is connected to the diagnostic link. The EHC control moduleactivates the fault display in the instrument cluster to alert the operator of the off-line sta-tus of the system. The EHC control module stores up to...
Page 25 - Place the vehicle on a level surface unloaded.
25 Level Control Systems DISplus/GT-1 Service Functions Program The Service Functions program of the DIS/MoDiC provides the Transport Mode activa-tion/deactivation and Ride Height Offset functions (see next page). Once the transport mode has been released, or if the system requires left to right sid...
Page 26 - TIS Repair Manual Information; 0 Troubleshooting (system troubleshooting charts)
26 Level Control Systems TIS Repair Manual Information The repair manual contains the following EHC specific sub-group repair information: • 00 General (general information, overview routing of pipes, tubes and components) • 12 Control and suspension system, rear (DIS referral, specific R&R proc...
Page 28 - System components; Pneumatic System of EHC2
28 Level Control Systems System components The X5 Two Axle Air Suspension System (EHC2) utilizes the air supply unit from EHCmounted in the luggage compartment, with the following components added or modified: • Air Supply Unit (with redesigned compressor and drier) • Pressure Accumulator • Valve Un...
Page 29 - Air Supply Unit
29 Level Control Systems 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 eli...
Page 30 - Compressor; Extended compressor ON time (180 seconds); Pressure Accumulator; Compressor with Drier
30 Level Control Systems 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 0 C. • Extended compressor ON...
Page 31 - Accumulator/Valve Unit
31 Level Control Systems The pressure accumulator decreases the load on the compressor and significantly reducesthe time required for large changes in ride height.The EHC 2 control module monitors system pressure via a pressure sensor mounted onthe accumulator. Normal system pressure is 15.7 +/- 0.7...
Page 32 - Ride Height Sensor; Rear Axle
32 Level Control Systems 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. The ride height sensor is an angle Hall sensor which is activated by a ring magnet. The ringmagnet is polarized vertica...
Page 33 - Air Suspension Strut
33 Level Control Systems Air Suspension Strut Rear Minor modifications were made to the rear axle air springs. The air springs and the dampersare configured separately at the rear axle. Front The air suspension replaces the steel suspension at the front axle, i.e. the spring bellows isattached to th...
Page 34 - Switch Assembly
34 Level Control Systems Switch Assembly The dash mounted switch assembly supplies a momentary switched ground to the EHC2Control 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 ...
Page 35 - Principle of Operation
35 Level Control Systems 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 ...
Page 37 - For safety-critical faults (vehicle is too high or at inclination); Control Modes
37 Level Control Systems In addition to the LED indicator, the following text messages canbe displayed in the instrument cluster: • T TR RA AIIL LE ER R M MO OD DE E A coupled trailer is identified via the trailer connector. To avoid damaging the trailer andthe vehicle, changes of vehicle level are ...
Page 38 - Sleep
38 Level Control Systems 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 leveland ...
Page 39 - Workshop Hints; The original level values are undershot at all four wheels,; Vehicle jack
39 Level Control Systems Workshop Hints If a threshold level is exceeded on all 4 wheels when the vehicle is stationary, the controlunit assumes that the vehicle has been raised on a workshop platform.There are three possible reset conditions for workshop platform recognition: • The original level v...
Page 40 - Important Workshop Hint
40 Level Control Systems 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 theworkshop platform must be refilled with air via the diagnostics. The activation proceduresmust also be repeated 6...
Page 41 - Two Air Springs
41 Level Control Systems Single Axle Air Suspension (E65/E66) Purpose of the System The single axle air suspension system used on the the E65/E66 is a further enhancementof the previous single axle air suspension system used on the the E39 and X5. The com-ponents used are similar to the Single Axle ...
Page 43 - Index
43 Level Control Systems Components (E65/E66) Air Supply Unit (LVA) The air supply unit is located in the spare tire recess and consists of the following compo-nents: • Protective cover with internal acoustic insulation • Lid • Rubber-mounted component carrier • Compressor Unit • Compressor Relay • ...
Page 44 - Control Unit; Vehicle Ride Height; EHC Module Location
44 Level Control Systems Control Unit The EHC control module is located in the right rear luggage compartment area in the mod-ule carrier next to the battery. On the E65/E66, the control module is connected to the K-CAN S. The EHC control module receives the following information: • Vehicle Ride Hei...
Page 46 - Check Control Messages; Cause; EHC
46 Level Control Systems Ride Height Sensor There are two ride height sensors, one for each rear wheel. The ride height sensor is actu-ated by a coupling rod and sends a signal to the EHC control unit. The sensor is a hall sensor which sends a DC Analog output voltage to the EHC module.The voltage r...
Page 47 - Control Mode Flow Chart
47 Level Control Systems Control Mode Flow Chart The following chart demonstrates the control sequences of the E65/E66 with single axlerear air suspension. Sleep Post Curve Lift Drive Normal Pre Kerb
Page 48 - Control Mode Overview
48 Level Control Systems Principle of Operation Control Mode Overview Control Modes Ongoing control operations are not affected by transitions from one mode to another.However, in the case of load cutout OFF, control operations are always concluded in orderto safeguard system deactivation. The contr...
Page 49 - Post Mode; There is no inclination identification in Pre-mode.
49 Level Control Systems Post Mode The Post-mode is adopted in order to compensate any inclination or to adjust the rideheight after driving and between the Pre-mode and Sleep mode. The Post-mode is limited in time to 1 minute. The Post-mode is only executed if the enginehas been running before the ...
Page 50 - Normal
50 Level Control Systems Normal The normal mode is the starting point for the vehicle’s normal operating state. It is obtainedby way of the engine running signal. Ride level compensation, changing the vehicle’s ride height and filling the accumulator arepossible. The compressor starts up as required...
Page 51 - Curve; The lateral acceleration is recorded by the rotation rate sensor.
51 Level Control Systems Kerb (Curb) Mode The Kerb mode prevents the inclination caused by the vehicle mounting an obstacle withine wheel from being compensated. Compensation would cause a renewed inclination ofthe vehicle and result in a renewed control operation after the vehicle comes off the obs...
Page 52 - Lift; Transport; New control units are supplied with the Belt mode set.
52 Level Control Systems Lift The Lift mode is used to prevent control operations when a wheel is changed or duringwork on the vehicle while it is on a lifting platform. This mode is recognized when the permitted rebound travel at one or more wheels isexceeded. For the E65/E66 the limit is > 55mm...
Page 53 - Operating Principle; Initialization/Reset Performance; Occurring faults are stored and displayed.; Control Sequence; The following stipulations are applicable here:
53 Level Control Systems Operating Principle Initialization/Reset Performance When the control unit is powered up after a reset (such as an undervoltage < 4.5 V or by aload cutoff), different tests and initializations are performed. This system is only enabledafter the tests have been successfull...
Page 54 - Safety Concept
54 Level Control Systems Safety Concept The safety concept is intended to inhibit any system malfunction, particularly unintentionalcontrol operations, through monitoring of signals and function relevant parameters. If faultsare detected, the system is switched over or shut down depending on the aff...
Page 55 - Ride Height Measurement; Diagnosis
55 Level Control Systems Workshop Hints Ride Height Measurement When checking vehicle ride height with EHC, measure from the lower edge of the wheelopening to the center of the wheel hub. Diagnosis Diagnostic items can be found in the “Control Unit Functions” path when using the DISplusor GT-1. The ...
Page 56 - Review Questions; The EHC control module on the E65/E66 is connected to the
56 Level Control Systems Review Questions 1. The EHC control module on the E65/E66 is connected to the Bus. 2. List the operating modes that are specific to the E65/E66 Air Suspension System: 3. Why is the accumulator needed on the dual axle EHC system? 4. List the components specific to the Dual Ax...
