Suspension - EHC Warning ON/No DTC's Stored

SI B37 01 03
Special Suspension Systems

July 2003
Service Engineering

Advance Information

SUBJECT
EHC Warning Illuminated, No Faults Stored

MODEL
E.39 Sport Wagon, E53 X5 (Vehicles with single axle air suspension)

SITUATION 1
The EHC warning stays illuminated afier the ignition is turned on. The text message "AIR SUSP INACTIVE" is displayed in the matrix of vehicles equipped with a high cluster. The suspension warning lamp is illuminated in vehicles with a low cluster. No faults are stored in the EHC control unit, and the air suspension system continues to work normally.

SITUATION 2
The EHC warning comes on while driving. No faults are stored in the control unit. The air suspension system continues to work normally.

Note:
Be aware that customers may miss when the actual warning was set, and complain that they notice it only when driving. In the majority of cases, the warning sets as in situation 1.

CAUSE 1
For situation 1, the "I'm OK" message of the BHC control unit fails to reach the Instrument Cluster. If the instrument cluster doesn't receive this message it will display the EHC warning indicator.

CAUSE 2
For situation 2, the EHC control unit detects a fault while driving and the fault code is currently not present when the vehicle is in the workshop for diagnosis. Sporadic fault codes can now be read from the shadow memory of the control unit.

CORRECTION 1 AND 2
The shadow memory of the control unit must be read out in order to check if faults have been detected previously.

To access the shadow memory:

^ Select Function Selection

^ Select Complete Vehicle

^ Select Chassis

^ Select Suspension and Damping Select Single Axle Air Suspension EHC

^ Select Special function for fault lamp sporadically on

^ Select Test Plan

Continue diagnosis by following the Test Plan. If you find faults in the shadow memory proceed with the appropriate Test Plan. If no fault codes are stored in the shadow memory, the EHC control unit must function will improve the communication timing of the "I'm OK" message.

WARRANTY INFORMATION
For information only.