service BMW X5 1999 E53 Level Control System Manual

23
Level Control Systems
Special Operating Modes
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.
Transport Mode
The vehicle rolls off the factory assembly line with the EHC control module in the trans-
port mode. The transport mode inflates the air springs to a higher position (approx.
30mm higher) than the normal mode in order to avoid damage during transit.
The system will not respond to any inputs that would alter the height of the vehicle. The
fault indicator (base cluster) is illuminated or instrument cluster matrix display (high clus-
ter) provides the message “Leveling System” to draw attention to the transport mode
setting.
The Service Functions section of the diagnosis program is used to activate/deactivate
the transport mode. Once the transport mode is deactivated, check the vehicle Ride
Height Offset making sure the vehicle rear axle height is to specification.
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.

24
Level Control Systems
EHC Service Information
Diagnosis/Coding
 The EHC control module is connected to the diagnostic link. The EHC control module
activates 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 three electrical/electronic
faults.
 Diagnosis/troubleshooting of EHC is carried out using the fault symptom troubleshoot-
ing program of the MoDiC or DIS. The EHC system has an extensive diagnosis program.
 Replacement control modules are shipped in the factory mode. The control modules
must be ZCS encoded using the DIS or MoDiC to activate the operating parameters.

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 side
height adjustment, the ride height "OFFSET" must be carried out to ensure that the vehi-
cles suspension has a base ride height level starting point.
The "HEIGHT OFFSET" is adjusted using the DIS or MoDiC. The procedure is as follows:
 Place the vehicle on a level surface unloaded.
 Access the Height Offset program in the service function menu.
 Measure the base ride height from the lower edge of the wheel housing to the center of
the wheel hub.
 Check measured height against the specifications listed
 Use the DIS/MoDiC to correct the ride height if the value differs from the listed specifi-
cation.

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 range is approximately .5 to 4.5 volts. The voltage increases with increasing
vehicle height and the nominal voltage at normal ride height is approximately 2.5 volts. The
right side rear sensor is a double sensor, the additional sensor is an input to the headlight
leveling systemand has it’s own power supply, ground and signal wires.
Check Control Messages
Control
UnitCauseVariable
Telltale IconCheck Control
MessageInformation in Control Display
EHC
Alive failure or
loss of function-
ality; transport
or belt mode setLevel Control
System failure“Level Control system failure”
Ground clearance and driving
comfort reduced. Avoid high
speed cornering. Have
checked by BMW Service as
soon as possible.
EHC
Level Control
System sensor
failure.Level Control
System Fault“Level Control System fault”
Possible reduction in driving
comfort. Have problem
checked by BMW Service.

55
Level Control Systems
Workshop Hints
Ride Height Measurement
When checking vehicle ride height with EHC, measure from the lower edge of the wheel
opening to the center of the wheel hub.
Diagnosis
Diagnostic items can be found in the “Control Unit Functions” path when using the DISplus
or GT-1. The functions available are Identifcation (ID page), Read/Clear Fault Memory, Read
Test Codes, Diagnosis Requests and Component Activation.
Service Functions
In the Diagnosis Program, there are numerous Service Functions that can be performed for
the E65/E66 EHC system. By entering into the “Function Selection” program and follow-
ing the “Chassis - Pneumatic Suspension” path all of the Service Functions are listed. The
Service functions include Ride-Level Offset, Transport Mode and Band Mode.