System functions: Notes

The following system functions of the single-axle electronic height control are described:

• Electronic height control 

  Ride height is controlled by air being fed into or withdrawn from the air springs. The EHC control unit receives information about the ride height on the left and right-hand sides of the vehicle from the level sensors.

  If the ride height is outside defined tolerances, the system will automatically activate the air supply unit to regulate to the specified level.

  The system is activated and starts to regulate whenever a door or the tailgate is opened. The system is deactivated after a certain time (approx. 20 minutes).

  The signals from the level sensors are filtered to distinguish between changes in load and other disturbances such as an uneven road surface. For correct use, two signals filtered at different frequencies are computed for each signal (low-pass filter with fast and slow filtering).

  Fast filtering is always employed when regulation is in progress. This prevents the regulated height from exceeding the specified level.

  Slow filtering is employed when the vehicle is in motion. This mode of filtering eliminates oscillations induced by the road surface.

  Both sides of the vehicle are regulated independently. In other words, the comparison of specification to actual value is performed separately for each side (exception: minimum height check in pre-mode and in "twist" control function. In these control functions, the mean value of the left and right-hand sides of the vehicle are considered).

  The EHC control unit recognizes the different operating conditions from the incoming signals and messages. Depending on operating conditions, appropriately adapted control functions are activated.

  The following control functions of the single-axle electronic height control are described:

  • Sleep mode
  • Pre-mode (temporary start/run-on)
  • Post-mode (readjustment)
  • Normal operation
  • Drive mode
  • Cornering
  • Twist
  • Level-up function (only E61 All-wheel drive until 09/2006)
  • Inclination detection after tire pressure loss (only E70, E71 with 8-cylinder engine or option 4UB "3rd row of seats")
  • Lifting platform
  • Transport mode
  • Production mode

    Transport and production modes can be set and cancelled with the BMW diagnosis system.

    If transport or production mode is set, "power economy mode active" will be stored in the fault memory.

The actual encoding data depend on the model series and vehicle equipment.