Driver Information Center Message

The ALC uses the instrument cluster for the display functions. When the suspension control module detects a fault that sets a DTC, it sends a message on the serial data line to the instrument cluster, which will display SERVICE LEVELING SYSTEM.

When a ride height change is requested by the customer a message will be displayed to indicate the vehicles selected height (Entry/Egress Ride Height, Normal Ride Height, Increased Ride Height, Raised 2 Ride Height) along with height transition indicators.

A 'Leveling Unavailable' DIC message does not necessarily indicate a problem with the air suspension. It is used when a change in ride height is unavailable due to vehicle parameters not being met. The 'Leveling Unavailable' message can occur due to any of the following:

• System cool down - Mostly due to system excessively used in a short amount of time.
• Low System Voltage - Minimum voltage to allow compressor operation is approximately 11 V.
• Tool Command Mode, Service Mode, or Alignment Mode Active - Indicated by an orange truck with a lock icon illuminated on the cluster. The system may place itself into "service mode" if one or more corners reach full rebound due to hoist / jack events, or some off-road driving events.
• Vehicle Loading Conditions - If the system determines that the vehicle mass is within a determined limit, the system will not allow some options such as Off-Road/ Raised selections.
• Trailer Mode Active - Some options such as off road options are not available when the vehicle is in Trailer Mode.
• Dynamic Detection - Vehicle is in a state that will not allow requested height changes due to dynamic conditions (hard turns, accelerations, decelerations, etc.).
• Recent loss of battery connection - If the message was displayed recently after a loss of battery or ECU connection, the system may take up to 30 min to allow some system operations.

A 'Service Leveling System/Speed Limited' DIC message does not necessarily indicate a problem with the air suspension system. It is possible the system has detected a state that has resulted a vehicle condition that has not been corrected within expected time limit. The conditions could be due to excessive front to rear rake, or side to side difference due to unexpected loading conditions, modified bent or broken suspension components.

If the vehicle does not see the correct conditions to complete a leveling event in the allowable time frame, the driver information center may display a message "Vehicle Too High Drive With Caution" message. If this occurs it may be due to excessive short stop and go driving events preventing the system from allowing a height adjustment. If this is seen the truck will need to remain stopped for approximately 30 seconds and the system will attempt a correction.

No System Response with no DTCs:

• The Leveling System operation is disabled when the hood or any of the doors are open (excluding rear hatch).
• Corner Side to Side Height Difference. This can be caused by uneven surfaces such as curbs, rocks, bent sensor linkage, broken suspension components, pressure imbalance.