The Quadra-Lift air suspension system provides height control and lifts the vehicle up to 4.1 inches from park mode to a best-in-class maximum ride height of 10.7 inches. Quadra-Lift is supported by four-corner air springs that provide a cushioned, premium ride. The front springs are a modular spring-over-shock design, very similar to a coil-over-shock design. Rear springs are stand-alone springs that are not incorporated with the shock absorber. Quadra-Lift operates automatically, or may be controlled manually via console controls. It can function independent of the Selec-Terrain system according to driver selection. The Quadra-Lift system became available on the Limited and Overland starting in July 2010 and on Laredo models starting in mid-October.
- Normal (NRH)
The standard ride height and is best for all-around driving conditions. It offers 8.1 inches of clearance and provides the most comfortable balance of ride and handling. The vehicle height will change automatically from Off-Road 1 to Normal when vehicle speed exceeds 50 mph. The vehicle height will change automatically from Aero to Normal when vehicle speed drops below 25 mph, or when vehicle speed is less than 60 mph and the user changes the Selec-Terrain switch from "Sport" to "Automatic".
- Off-Road 1 (OR1)
Provides 1.3 extra inches (9.4 inches of clearance) for off-roading, but allows a bit more suspension comfort. This position provides a good balance between ground clearance and ride comfort. This position should be the default position for all off-road driving until OR2 is needed. A smoother and more comfortable ride will result. Press the "Up" button once from the NRH position while the vehicle speed is below 48 mph (77 km/h). When in the OR1 position, if the vehicle speed remains between 40 mph (64 km/h) and 50 mph (80 km/h) for greater than 20 seconds or if the vehicle speed exceeds 50 mph (80 km/h), the vehicle will be automatically lowered to NRH.
- Off-Road 2 (OR2)
Provides the maximum ride height of 2.6 extra inches (10.7 inches of ground clearance) for the highest clearance over obstacles. This position also provides the best approach, departure, and breakover angles. To enter OR2, press the 'Up' button twice from the NRH position or once from the OR1 position while vehicle speed is below 20 mph (32 km/h). While in OR2, if the vehicle speed exceeds 25 mph (40 km/h) the vehicle height will be automatically lowered to OR1.
Lowers the vehicle just over a half inch to maximize aerodynamics and fuel economy at highway speeds. This position also reduces body roll and provides a "sportier" feel. The vehicle will automatically enter Aero Mode when the vehicle speed remains between 62 mph (99 km/h) and 66 mph (106 km/h) for greater than 20 seconds or if the vehicle speed exceeds 66 mph (106 km/h). The vehicle will return to NRH from Aero Mode if the vehicle speed remains between 30 mph (48 km/h) and 35 mph (56 km/h) for greater than 20 seconds or if the vehicle speed falls below 30 mph (48 km/h). The vehicle will enter Aero Mode, regardless of vehicle speed if the Selec-Terrain™ knob is turned to the "SPORT" position. Turning the Selec-Terrain™ knob to the "AUTO" position will return the system to normal operation.
Lowers the entire vehicle 1.5 inches below normal height to make loading and unloading people or cargo much easier. To enter Park Mode, press the "Down" button once while the vehicle speed is below 25 mph (40 km/h). Once the vehicle speed goes below 15 mph (24 km/h) the vehicle height will begin to lower. If the vehicle speed remains between 15 mph (24 km/h) and 25 mph (40 km/h) for greater than 60 seconds, or the vehicle speed exceeds 25 mph (40 km/h) the Park Mode change will be cancelled. To exit Park Mode, press the "Up" button once while in Park Mode or drive the vehicle over 15 mph (24 km/h).
The Selec-Terrain™ switch will automatically change the vehicle to the proper height based on the position of the Selec-Terrain™ switch. The height can be changed from the default Selec-Terrain™ setting by normal use of the air suspension buttons. Refer to "Selec-Terrain™" in "Starting and Operating" for further information.
The system requires that the engine be running for all changes. When lowering the vehicle all of the doors, including the liftgate, must be closed. If a door is opened at any time while the vehicle is lowering the change will not be completed until the open door(s) is closed.
The Quadra-Lift air suspension system uses a lifting and lowering pattern which keeps the headlights from incorrectly shining into oncoming traffic. When raising the vehicle, the rear of the vehicle will move up first and then the front. When lowering the vehicle, the front will move down first and then the rear.
After the engine is turned off, it may be noticed that the air suspension system operates briefly, this is normal. The system is correcting the position of the vehicle to ensure a proper appearance.
To assist with changing a spare tire, the Quadra-Lift air suspension system has a feature which allows the automatic leveling to be disabled. Press and hold both the "Up" and "Down" buttons simultaneously between 5 and 10 seconds, a message will appear in the EVIC stating leveling has been disabled immediately after both buttons have been released. Refer to "Electronic Vehicle Information Center (EVIC)" in "Understanding Your Instrument Panel" for further information. Driving the vehicle over 5 mph (8 km/h) will return the air suspension to normal operation.
Quadra-Lift is a closed system so adjustments are much faster than other systems that must draw in or exhaust air for operation. It is the first SUV to use the latest air suspension technology utilizing a closed type design.
The closed type system does not draw in fresh air during vehicle lifting or leveling-up, or pump air out to the atmosphere during lowering or leveling down. Instead it moves stored pressurized air from the reservoir to the air springs and back again.
Since the system's compressor is working with pre-pressurized air, and not air at atmospheric pressure, the compressor can be smaller which translates into reduced power consumption and weight as well as improved NVH characteristics. Pressurized air is moved between the reservoir and the springs by way of an air supply unit (ASU). The ASU consists of an air compressor and a valve block assembly that is plumbed to the springs with a network of lines. The ASU valve block provides six color-coded pneumatic connections to the system. Four connections distribute or retrieve air from each of the air springs. One connection is the inlet from the compressor, and the last connection exhausts the system. The ASU also contains an intake / exhaust assembly with filter, onboard desiccant, a reversing valve, a temperature sensor, and a pressure sensor. It is important to note that the ASU is not designed to fill an empty system. The ASU's main function is to pressurize and move air that is already there.
Front and rear height sensors measure the distance between the body and suspension, and provide feedback to the control system to constantly monitor vehicle height. The air suspension control module (ASCM) contains the logic that controls ride height during all driving and loading conditions. The ASCM controls the ASU compressor and valve block, and is influenced by many other modules and systems. The powertrain control module (PCM), anti-lock brake system (ABS) control module, cabin compartment node (CCN), and drivetrain control module (DTCM) are all primary inputs to the ASCM.
By working with pre-pressurized air, the closed air suspension system also provides additional benefits to the customer:
A message will be displayed on the EVIC indicating the compressor is cooling down and there will be a diagnostic trouble code (DTC) set. The DTC in the ASCM module does not necessarily indicate service is needed. If the EVIC message and DTC occurs often, it may be an indication of a leak in the system.
Whether the air suspension system is operating normally or has a system fault, the electronic vehicle information center (EVIC) continuously displays status messages to alert the owner or technician. During normal operation, there are five "level achieved" messages that correspond to the five unique air suspension system heights - or modes.
The raising or lowering icon appears when the system changes from mode to mode. For example, when changing from normal to the aerodynamic ride height, the air suspension lowering icon displays until feedback from the height sensors indicates the aerodynamic ride height is achieved. The "aerodynamic ride height" message displays.
Additionally, there are several inputs to the air suspension control module that prevent the air suspension system from changing modes. Vehicle speed that is excessive or too low prevents certain modes from being achieved and a message displays. If doors are open when the user requests to lower the vehicle, a message displays and the air suspension does not lower until the doors are closed. Excessive air supply unittemperature also disables the air suspension system until the compressor cools down to safe operating levels. And finally, depending on the severity of the failure, one of two messages displays if a fault is detected by the air suspension control module.
Diagnosis and repair of the Grand Cherokee's air suspension system may require the use of the wiTECH "system tests" tab to run programs that test the system or to run one of many routines from the "miscellaneous functions" tab that place the system into a mode suitable for service.
The first step in diagnosing air suspension system concerns is to cycle the system through its modes during a road test, while monitoring the EVIC for feedback. If the road test indicates the system is not operating as designed, the wiTECH scan tool application is used to interrogate the air suspension control module. The ASCM operates on the CAN-C network and is displayed in wiTECH's network topology screen.
Before working under the vehicle, it is necessary to disable the Quadra-Lift system to prevent unintended raising or lowering of the suspension, which is a potential safety concern. To temporarily disable the Quadra-Lift system, press and hold the suspension up and suspension down buttons simultaneously for 5 to 10 seconds. A message appears in the EVIC indicating that the Quadra-Lift system has been disabled. This is one of many reasons why following service and diagnostic information is critical.
Use of the scan tool is instrumental in the diagnosis and repair of Quadra-Lift system concerns. There are several Quadra-Lift system tests and service routines that are performed using the scan tool. Many routines are helpful tools that can make diagnosing Quadra-Lift suspension concerns easier. The scan tool is also needed to prepare the system for service or to adjust system settings after a repair has been made.
Refilling the System
If 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.
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