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Level Control Systems

Air Suspension Systems (EHC)

Purpose of the System

Air Suspension systems were first introduced on the 1999 E39 Sportwagon. Since then

the E53 (X5) and E65/E66 (7Series) models were available with this new system. EHC are

available is two configurations, the Single Axle Air Suspension System and the Dual Axle

Air Suspension System. The Dual Axle (EHC II) system is only available on E53 X5 models

from the 2002 model year.

EHC systems can be found on the following vehicles:

• E39 Sportwagon 528i, 525i and 540i from the 1999 Model Year (Single Axle)

• E53 X5 3.0i and 4.4i from the 2000 Model Year (Single Axle)

• E53 X5 4.6iS from 2002 (Single Axle)

• E53 X5 3.0i and 4.4i from 2002 (Dual Axle EHC II)

• E65/E66 from 2003 Model Year (Single Axle)

There are some functional changes with these systems. On EHC, the entire axle load is

borne by the air suspension. The underlying control philosophy of EHC is “Control only

when absolutely necessary”. This means that brief changes in the ride height are not com-

pensated (such as potholes). This avoids any unnecessary control operations.

The advantages of air suspension are as follows:

• Control is independent of the vehicle engine

• Single-wheel control is possible

• Lateral locking is affected

• A distinction is made between load and drive states

• An inclined load is identified and corrected

• However, an inclination is not compensated

• Self diagnosis can be performed

• Diagnosis with DISplus or GT-1 is possible

• An automatic interruption of control takes place in case of cornering and wheel

changes.

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BMW 740iL Reparaturanleitung Seite 13