2005 BMW X5 Ride height sensor

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EHC System Components
Control Module
The Control Module is mounted in the module carrier box in the luggage compartment on
the right side. It contains the processing electronics and final stages for operation of the
EHC system.
The control module receives the follow-
ing inputs for its processing functions:
• KL 30 & 31 (Power/Ground)
• KL 15
• Left & Right Ride Height Sensors
• K Bus for;
- Vehicle speed
- Engine running
- Door/tailgate - open/closed
The control module incorporates two filters (slow/rapid) for processing the input signals
from the ride height sensors. Depending on the operating mode, either the slow or rapid fil-
ter is used to check the need for a regulating sequence.
The slow filter is used during the normal operation mode to prevent normal suspension trav-
el from causing the system to make adjustments.
The rapid filter is used during the pre-run and tailgate (LID) modes to ensure that the sus-
pension is adjusted quickly while the vehicle is being loaded or checked prior to operation.
12530012

Air Springs
The air spring is made from a flexible rubber material. It
forms an air tight cavity which provides the calculated spring
rate required for the sport wagon.
As the spring compresses downward the bottom edge of
the rubber material rolls along the vertical surface of the
base mount cylinder.
Air is added or removed from the air spring through its top
port. The top port of each spring is connected to a reser-
voir and the air supply pipes. The reservoirs are required to
hold additional air due to the compact design of the springs.
Rear Axle Level Sensors
Hall effect sensors are mounted on the left
and right sides of the rear suspension for ride
height detection. They are pivoted by a cou-
pling rod through the rear axle swing arms.
The hall sensors produce a varying voltage
input to the control module as the suspension
height changes.
If the vehicle is equipped with Xenon head-
lights the right side sensor contains an addi-
tional sensor for the automatic headlight level
adjustment system.
Warning Display
If the system is faulted and off-line or set in the transport mode, the following is displayed:
High Cluster: A message is posted in the high cluster matrix display.
E39 Features 07
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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/Post-Run Mode
 Normal Mode
 Tailgate Mode
Two special operating modes are also included in the control module programming.
 New/replacement mode(pre ZCS encoded). This mode provides basic operation.
 Transport Mode - Transport mode is set at the factory and raises the vehicle 30mm to
prevent vehicle damage during transportation. It must be deactivated with the DIS/
MoDiC prior to customer delivery.
Pre-Run/Post-Run Mode
The Pre-Run mode is activated when the vehicle is parked and the control module is in the
sleep mode. Opening a door or the tailgate initiates a system wake up and the control mod-
ule comes on-line.
The control module performs a self-check of the control electronics and sensors. If no fault
is found, the system will check the ride height and institute a rapid regulation if the height
varies by more than 40mm.

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Normal Operation Mode
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 constantly
monitor the input signals from the ride height sensors and will activate a correction if the
ride height deviates by at least 10mm.
Tailgate Operating Mode
The tailgate operating mode is activated if the gate is opened with KL - 15 On and the
engine running. The difference between this mode and the normal operating mode is the
response time is rapid instead of slow .

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Special Operation Mode
• Assembly Line Mode (New control module)
The assembly line mode refers to control module manufacturing. New control modules
are stored in a deactivated state. The control programming is not active and must first
be ZCS encoded.
After installing a replacement control module, it must be coded using the DIS or MoDiC.
The instrument cluster fault display will remain illuminated until the control module is
coded.
Control Interrupts
Cornering
To prevent unnecessary suspension adjustments while driving through corners, a “control
interrupt” is built into the system. Above 30MPH the control module monitors the left/right
ride height sensors for a difference of 30mm. Exceeding this difference will put the system
into a control interrupt and no adjustment will take place. The control interrupt last for a
duration of 5 minutes.
Vehicle Lifting
The ride height control is interrupted when the vehicle is raised on a lift or with a jack. The
system monitors the ride height sensor inputs and when the height limit of 90 mm is
exceeded, the control is switched OFF until the vehicle is lowered again.