Operation
OPERATION
Special Tools:
WARNING:
All pressurized air suspension components contain high pressure air (up to 220 psig). Use extreme caution when inspecting for leaks. Wear safety goggles and adequate protective clothing when inspecting or servicing the air suspension system. A sudden release of air under this amount of pressure can cause possible serious or fatal injury.
WARNING:
Support the vehicle by supplemental means before performing any work on the air suspension system to prevent the vehicle from changing height. Before any given component is to be serviced it must be deflated. Servicing the air suspension system without supplemental support, or with pressure in the specific component, can cause possible serious or fatal injury.
CAUTION:
When removing an air line from a component and the air line is to be reused, do not remove the 90° fitting or the brass fitting from the air line. If either is removed, the air line must be replaced. New components have air line fittings attached; however if the original air line is used the original fitting must also be used. Do not remove protective caps or plugs from air lines or components until ready to install the air line to prevent moisture or dirt intrusion. All air line fittings must be hand started to avoid cross threading.
NOTE:
The air suspension system will auto-disable when lifted on a frame hoist, or when jacking one corner of the vehicle. The air suspension may attempt to change height slightly prior to switching to auto-disable. A manual disable is also available by pressing the "Up" and "Down" switches of the terrain select switch simultaneously for more that 5 seconds. The air suspension system will return to normal operation when the vehicle speed reaches 25 kph (15 mph).
NOTE:
The air suspension system will not lower if any of the doors or liftgate is open (normal operation) or the engine is not running. Doors and liftgate status are ignored when using a scan tool.
NOTE:
When the Air Suspension Control Module (ASCM) or any height sensor is replaced the ASCM will need to be initialized using a scan tool. Refer to the appropriate installation procedure for specific instructions.
General InformationThe air suspension system is designed to raise and lower the vehicle height as required depending on driver request using the terrain select switch, or automatically with the terrain select switch in the Auto position. There is an Air Suspension Control Module (ASCM) located under the driver's seat which contains the logic and controls for the system. Multiple modules work together to increase vehicle stability and traction along with vehicle ride height. The ASCM uses several Controller Area Network (CAN) data bus systems for inputs and outputs of the information necessary for the different systems to operate. The use of a scan tool is necessary for diagnostics, and replacement of any pressurized components. Height sensors on each corner of the vehicle monitor the vehicle height. The front of the vehicle is raised/lowered with two air suspension spring and shock assemblies, and the rear uses two air suspension springs.
The air suspension is a closed type system that does not draw in fresh air during vehicle lifting or leveling. Instead, it moves pressurized air back and forth between an air suspension reservoir and the four air springs as required to raise or lower a specific corner of the vehicle. The air suspension compressor assembly includes an air suspension valve block, controlled by the ASCM. The valve block isolates and actuates the raising and lowering of each pressurized component using individual air lines for the air springs and reservoir. The air suspension compressor does have a filtered air suspension hose assembly for adding air volume if a component of the system loses its air pressure and is replaced. The compressor is not intended to replenish the entire systems air volume. There is a procedure for complete system fill using an external source if it is necessary; however, this should only be necessary if the air suspension compressor or air compressor valve block is replaced.
Refilling the SystemIf the air suspension system is fully depleted of air it can be refilled using a scan tool and Air Suspension Refill Tool - (10247) which is used with a nitrogen supply tank (can be acquired at a local gas supplier). The nitrogen must be Purity Class 5 (99.999% pure). The size and volume of the nitrogen supply tank will determine how many air suspension systems can be filled.
Changing Ride Height
Using the up and down switch, ride height can only be changed while the air suspension system is in normal operating conditions. Air suspension system normal operating conditions are as follows:
- Scan tool disconnected
- All doors closed
- Engine running
- Minimum battery voltage greater than 10.5 volts
Using a scan tool, ride height can be changed regardless of the engine state (running or not), doors (open or closed). The only condition necessary is that battery voltage must be greater than 10.5 volts.
Ride Heights for Suspension Measurements or Adjustments When checking or performing an alignment the air suspension system must be in the wheel alignment mode or the Aero mode if using a scan tool. When measuring curb height, the air suspension system must be in the manually selected "Aero Mode" position. or the Normal Ride Height (NRH) mode if using a scan tool.
Manual Control An up and down switch is located on the center stack for driver control of the system. When the driver presses the up and down switch to manually raise or lower the vehicle height the Electronic Vehicle Information Center (EVIC) displays a vehicle "up" or "down" message icon and a LED indicator on the switch changes position. The EVIC displays the current position of the vehicle when it is achieved. When lowering the vehicle, the front is always first to move. When raising the vehicle, the rear is always the first to move. When the ASCM receives a command to change the vehicle more than one ride height position the action is performed in multiple steps. If request to change by two positions the rear will raise one position, then the front will raise one position, the rear again raises one position, then the front will raise to the final position. If requested to lower more than one position the same steps happen, EXCEPT the front moves first. This multi-step motion controls the angle the headlights are projected by controlling the pitch of the vehicle, keeping them from going above their normal projection plane.
There are five predetermined manual height settings; Normal Ride Height (NRH), two above and two below NRH. The predetermined vehicle heights (above or below NRH) are as follows:
- Off-Road 2 (OR2), + 51 mm (2.0 in.)
- Off-Road 1 (OR1), + 30 mm (1.2 in.)
- Aero Mode, - 28 mm (-1.1 in.)
- Entry/Exit Mode, - 53 mm (-2.1 in.)