Hummer H2. Manual - part 2228

Fig. 44: Disconnecting Air Lines Procedure 
Courtesy of GENERAL MOTORS CORP. 

3. Disconnect all air lines using the following procedure. Air spring connection shown. All others are 

similar. 

1. Push the air supply line into the air spring connection and hold in place.  

2. Depress and hold the air supply line collet (2) down.  

3. Remove the air supply line (1) from the air spring.  

4. For air lines that are integral to a wiring harness. Trim off air line at the wiring harness with a sharp 

cutting tool. Leave the remaining air line in the wiring harness.  

Installation Procedure 

IMPORTANT: Inspect the ends of all air supply pipes for deep scoring and sharp edges 

before reinstalling the pipe to the fitting. Replace any pipe that exhibits 
any of the above conditions.

 

2004 Hummer H2 

2004 SUSPENSION Air Suspension - Hummer H2

  

Fig. 45: Installing Air Line 
Courtesy of GENERAL MOTORS CORP. 

1. Install air line to the appropriate fitting until the line bottoms. 

2. Pressurize the air springs. Refer to Air Suspension Pressurization Procedure .  

3. Lower vehicle.  

4. Start the vehicle and run for approximately 2 minutes to verify that the air suspension system is 

functioning properly.  

DESCRIPTION AND OPERATION 

AIR SUSPENSION DESCRIPTION AND OPERATION 

Air Suspension 

IMPORTANT: If the rear axle was allowed to hang unsupported, lower the vehicle far 

enough to allow the air spring to be manually engaged to the support on 
the axle tube with minimal distortion of the air spring bladder. Ensure that 
the air spring is fully engaged to the axle support.

 

2004 Hummer H2 

2004 SUSPENSION Air Suspension - Hummer H2

  

The primary mission of the air suspension system is the following for the rear suspension under loaded and 
unloaded conditions: 

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Keep vehicle visually level  

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Maintain optimal ride height  

The Air Suspension System consists of the following items: 

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Air Suspension Compressor Assembly  

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Air Suspension Module  

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Electronically Controlled Air Suspension Relay  

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Air Suspension Sensors  

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Ride Height Switch  

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Air Suspension Exhaust Valve  

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Air Suspension Inflator switch and fill valve  

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Air Suspension Pressure Sensor  

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Air Suspension Inlet Valves  

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Rear Air Springs  

Compressor Assembly 

The air compressor is a positive displacement air pump, powered by a 12 V DC permanent magnet motor. A 
thermal limit switch protects the compressor. The thermal limit switch is normally closed and provides a ground 
signal to the air suspension module. If there is an overtemperature condition the thermal limit switch will open 
and signals the air suspension module to deactivate the compressor relay. The compressor will stop running and 
a DTC will set. Intake air for the compressor is drawn through an intake filter and line that is attached to the 
fuel filler pipe in the left rear wheel area. The air compressor assembly is mounted to a bracket that is located 
under the rear center of the vehicle. The compressor air dryer is mounted next to the air compressor. It contains 
a moisture absorbing chemical that drys the compressed air before it is delivered to the rear air springs. 
Moisture is removed from the dryer and returned to the atmosphere when air is exhausted from the air springs 
during vehicle lowering. 

Air Suspension Module 

The air suspension module will conduct several self test at every ignition activation, while other test do not 
commence until wheel speed is detected at the wheel speed sensors. During self test if any of the module 
components are found to be malfunctioning a DTC will set and the corresponding telltale is activated. The 
telltale message that the air suspension module can display is SERVICE SUSPENSION SYSTEM. Each DTC 
consists of one current and one history DTC. History codes will be cleared after 100 consecutive malfunction 
free ignition cycles or with a scan tool. The air suspension module communicates with other modules in the 
vehicle via class 2. There is a standby feature in the air suspension module whereby downward leveling is 
possible for 30 minutes after the ignition has been turned off. This is to allow the vehicle to level after a load 
has been removed. The leveling function will be disabled when any door or liftgate is open or when the inflator 
is being used. To prevent energizing the electronically controlled air suspension relay or air suspension inlet 
valves during normal ride motions the air suspension module provides a calibrated delay before leveling the 

 

2004 Hummer H2 

2004 SUSPENSION Air Suspension - Hummer H2

  

vehicle. 

Electronically Controlled Air Suspension Relay 

The compressor is controlled by the air suspension module by the use of a relay. The relay and wiring are 
protected with a 60-amp fuse. The air suspension module will only activate the compressor relay when the 
engine is running. 

Air Suspension Sensors 

The rear air suspension sensors are potentiometers which detect height changes at the rear of the vehicle. The 
sensors relay the height changes to the air suspension module. The sensors are mounted to the frame at the rear 
wheel area on the left and right sides. The activation arm is attached to the upper control arms of the rear 
suspension. 

Ride Height Switch 

Extended ride height is used to increase vehicle ground clearance. When the ERH switch is activated the vehicle 
will raise 2 inches at the rear. The extended ride height will only occur if vehicle speed is less than 64 km/h (40 
mph) with the liftgate and all doors closed with the engine running. When the switch is activated the switch 
LED will flash while the vehicle is transitioning to extended ride height. When the vehicle reaches extended 
ride height switch LED will be on continuously. The vehicle will return to normal height when the switch is 
activated again and the switch LED will go off. The vehicle will automatically return to normal height if vehicle 
speed increases over 64 km/h (40 mph) and the switch LED will turn off. 

Air Suspension Exhaust Valve 

The air suspension exhaust valve is used to exhaust air from the air springs and lower the vehicle. The air 
suspension exhaust valve is mounted on the head of the compressor. The air suspension exhaust valve is 
controlled by the air suspension module. 

Air Suspension Inflator Switch and Fill Valve 

The inflator system consist of a inflator hose to provide a means of inflating objects and a switch with a LED 
located in the rear compartment. The inflator will only function when the engine is running and the vehicle is in 
park. The switch LED will be illuminated with the inflator on. The inflator function will have priority over 
leveling functions. 

Air Suspension Pressure Sensor 

The air suspension system uses the air pressure sensor to monitor system pressure. The air suspension module 
uses that signal to determine if there is a leak in the system and to maintain a minimum air pressure in the 
system. 

Air Suspension Inlet Valves 

The air suspension system has two inlet valves. One for the right air spring and one for the left air spring. The 
valves are mounted to the valve block with the air suspension pressure sensor and is located next to the 

 

2004 Hummer H2 

2004 SUSPENSION Air Suspension - Hummer H2