Electronic Suspension System - Automatic Level Control Buick LeSabre VIII

FASTENER TIGHTENING SPECIFICATIONS

Fastener Tightening Specifications

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DIAGNOSTIC STARTING POINT - AUTOMATIC LEVEL CONTROL

Begin the system diagnosis with the DIAGNOSTIC SYSTEM CHECK - AUTOMATIC LEVEL CONTROL . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system.
2. The ability of the control module(s) to communicate through the serial data circuit.
3. The identification of any stored Diagnostic Trouble Codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2 Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3 The symptom list in Symptoms will determine the correct diagnostic procedure to use.
3. 4 The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

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SCAN TOOL DATA DEFINITIONS

1. Accum Fault- Compressor Defined period of time the compressor is active with out an exhaust cycle.
2. ALC Compressor Active Indicates when the compressor is running.
3. ALC Exhaust Solenoid Active Indicates when the exhaust solenoid is on.
4. ALC Relearn This procedure reprograms the RIM with the ride height specification, per the suspension option.
5. Battery Low-Compressor This indicates when there is low voltage at compressor.
6. Calibration I.D. This number designates the modules calibration.
7. Exhaust Defined period of time that the exhaust is active with out a compressor cycle.
8. Filtered Position Valve As the vehicle operates the suspension position sensor is monitored, and the information is filtered, to the RIM so it can adjust the suspension.
9. Leveling Sensor Feed Voltage feed to the suspension position sensor.
10. Progress Fault- Compressor Defined period of time the that the compressor is active, and a change is not detected by the sensor.
11. Progress Fault- Exhaust Defined period of time that the exhaust is active and no change is detected at the sensor.
12. Prom I.D. The modules internal "PROM" identifier.
13. Suspension Position Sensor Indicates the sensor signal voltage to the control module.
14. Trim Value A value programed in the RIM.

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DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

Circuit Description

The automatic level control sensor is a potentiometer. The RIM determines the height of the rear of the vehicle based on the voltage from the automatic level control sensor. The RIM raises or lowers the rear of the vehicle in order to keep the vehicle level.

Conditions For Running DTC

The RIM is powered up and DTC B1327 is not set.

Conditions For Setting DTC

1. The automatic level control signal voltage is less that 0.3 V or greater than 4.8 V.
2. The above conditions are present for greater than 10 seconds.

Action Taken When DTC Sets

The automatic level control suspension will be inoperative.

Conditions For Clearing DTC

The RIM does not detect a voltage above or below the predetermined value during the diagnostic self test.

Diagnostic Aids

Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS and TESTING FOR ELECTRICAL INTERMITTENTS in Wiring Systems.

The numbers below refer to the step numbers on the diagnostic table.

1. 4 Tests for the proper operation of the circuit in the high range. If the fuse in the jumper opens when you perform the test, the signal circuit is shorted to ground.
2. 5 Tests for a short to voltage in the 5-volt reference circuit.

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The automatic level control sensor is a potentiometer. The RIM determines the height of the rear of the vehicle based on the voltage from the automatic level control sensor. The RIM raises or lowers the rear of the vehicle in order to keep the vehicle level.

The RIM detects a short to battery voltage on the reference or signal circuit.

The leveling sensor input or feed circuit is found to be shorted to battery voltage for more than 10 seconds.

The automatic leveling control will be disabled.

When the RIM does not detect voltage out of the specified range in the signal or reference circuit during the diagnostic self test.

Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS and TESTING FOR ELECTRICAL INTERMITTENTS in Wiring Systems.

The numbers below refer to the step numbers on the diagnostic table.

1. 6 Make sure the good ground used is separate from the grounds used by the Rear Integration Module.

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The automatic level control adjusts the vehicle suspension ride height. The RIM determines the height of the vehicle based on the voltage from the automatic level control sensor. The RIM raises and lowers the rear of the vehicle in order to keep the vehicle level.

1. The RIM is powered up.
2. DTC B1327 is not set.

The exhaust valve solenoid output is found to be open or shorted to ground for 10 seconds.

The automatic level control will be inoperative.

When the RIM does not detect a failure during the self test.

1. Inspect for the addition of any aftermarket components.
2. Inspect all wiring carefully for chaff's and proper routing. Refer to «TESTING FOR INTERMITTENT & POOR CONNECTIONS»(/buick/lesabre/viii-2000-2005/remont/accessories-control-systems/#wiring-systems-general-information__testing-for-intermittent-poor-connections) and «TESTING FOR ELECTRICAL INTERMITTENTS»(/buick/lesabre/viii-2000-2005/remont/accessories-control-systems/#wiring-systems-general-information__testing-for-electrical-intermittents) in Wiring Systems.

The numbers below refer to the step numbers on the diagnostic table.

1. 2 Listen for an audible click when the exhaust solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 5 Tests if ground is constantly being applied to the solenoid.

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The automatic level control adjusts the vehicle suspension ride height. The Rim determines the height of the vehicle based on the voltage from the automatic level control sensor. The RIM raises and lowers the vehicle in order to keep the vehicle level.

1. The RIM is powered up.
2. DTC B1327 is not stored.

The exhaust valve output is found to be shorted to battery.

The automatic level control will be inoperative.

The RIM does not detect a failure during the self test.

1. Inspect for the addition of aftermarket components.
2. Inspect all wiring harnesses carefully for chaff's and proper routing.
3. This circuit is monitored every 3 milliseconds. If the exhaust valve solenoid is found to shorted to battery for 10 milliseconds (100th of a second) the code will be stored as current.

The numbers below refer to the step numbers on the diagnostic table.

1. 2 Listen for an audible click when the solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3 Tests the exhaust valve solenoid circuit for proper operation.
3. 4 Tests the control circuit for a short to voltage.

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SYMPTOMS - AUTOMATIC LEVEL CONTROL

Note. The following steps must be completed before using the symptom tables.

1. Perform the «DIAGNOSTIC SYSTEM CHECK - AUTOMATIC LEVEL CONTROL»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control module(s) can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «AUTOMATIC LEVEL CONTROL DESCRIPTION & OPERATION»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Automatic Level Control System. Refer to «CHECKING AFTERMARKET ACCESSORIES»(/buick/lesabre/viii-2000-2005/remont/accessories-control-systems/#wiring-systems-general-information__checking-aftermarket-accessories) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «AIR COMPRESSOR LEAK TEST»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control__air-compressor-leak-test)
2. «AUTOMATIC LEVEL CONTROL SYSTEM LEAK TEST»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control)
3. «REAR OF VEHICLE HIGH»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control)
4. «REAR OF VEHICLE LOW»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control)

AIR COMPRESSOR LEAK TEST

Note. Tools Required: Pressure Gage (0-300 psi) (J 22124-B) and Pressure Gage Adapter (J 22124-91).

1. Attach the J 22124-91 to the air dryer.
2. Attach the J 22124-B to the J 22124-91 with the toggle valve on the opposite side of the air compressor. Close the toggle valve.
3. Apply air pressure at the Schrader valve. Pressurize until the J 22124-B reads 690 kPa (100 psi).
4. Check the following areas using soap bubbles: Solenoid valve - Replace the air compressor head if leaking. Air dryer to compressor head O-ring - Replace the air dryer if leaking. Air dryer cover - Replace the air dryer if leaking. Air compressor head gasket - Replace the air compressor head if leaking. Air compressor head cover gasket - Tighten the cover bolts to 5.6 N.m (50 lb in) if the head cover gasket is leaking. If the leak persists, replace the air compressor head.

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Removal Procedure

1. Remove the air compressor assembly with the bracket from the vehicle. Refer to «AIR COMPRESSOR REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
2. Rotate the spring clip 90 degrees out of the slot.
3. Remove the air dryer from the air compressor assembly.
4. Remove the seal from the air compressor.

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Installation Procedure

Note. Lubricate the seal with silicone lubricant. The spring clip must not be in the slots of the air compressor.

1. Install a new seal onto the air dryer.
2. Install the air dryer with the seal in the air compressor.
3. Rotate the spring clip 90 degrees to lock the air dryer in place.
4. Install the air compressor assembly with the bracket onto the vehicle. Refer to «AIR COMPRESSOR REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .

1. Raise the vehicle. NOTE: Before disconnecting the air hose from the intake air filter or the air compressor, clean the components and the surrounding area to prevent dirt and other foreign material from entering the air compressor.
2. Disconnect the intake air filter from the body rail and the air hose.
3. Slide the air compressor connector off of the connector anchor.
4. Remove three bolts and the heat shield from the air compressor bracket.
5. Disconnect the air hose from the air compressor assembly at two places.

1. Connect the air hose to the air compressor assembly at two places.
2. Connect the intake air filter to the air hose and the body rail. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Install the heat shield and the harness tie with three bolts. Tighten three bolts to 4 N.m (35 lb in).
4. Install the air compressor connector onto the connector anchor.
5. Lower the vehicle.

1. Raise the vehicle.
2. Remove the wheel from the vehicle. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels.
3. Disconnect the height sensor connector.
4. Disconnect the sensor link from the ball stud.
5. Loosen the sensor mounting nut.
6. Disengage the anti-rotation tab and slide the sensor downward.
7. Remove the sensor from the vehicle.

1. Insert head of the sensor mounting stud into the key hole.
2. Slide the sensor upward until the anti-rotation tab engages in the lower hole. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
3. Tighten the sensor mounting nut. Tighten the nut to 9 N.m (80 lb in).
4. Connect the sensor link on the ball stud.
5. Connect the height sensor connector.
6. Install the wheel on the vehicle. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels.
7. Lower the vehicle.

Disassembly Procedure

1. Remove the air compressor assembly from the vehicle. Refer to «AIR COMPRESSOR REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
2. Remove the air compressor connector from the connector anchor (slide the air compressor connector away from the air compressor and off of the anchor).
3. Remove the two bolts and the heat shield from the air compressor bracket.
4. Remove the air dryer. Refer to «AUTOMATIC LEVEL CONTROL AIR DRYER REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
5. Cut the harness tie.
6. Remove the bolt and the harness tie. NOTE: Note the wire colors and the terminal numbers to ensure correct assembly.
7. Remove the two harness ties and the wrap from the wires.
8. Remove two wire terminals from the air compressor connector.
9. Remove the air hose from the air compressor head.
10. Remove the three head bolts and the air compressor head from the air compressor assembly.
11. Remove the gasket from the air compressor head or the air compressor assembly.

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1. Install the new gasket on the air compressor assembly. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the air compressor head on the air compressor assembly with the three bolts. Tighten the three bolts to 6 N.m (53 lb in).
3. Connect the air hose to the air compressor head.
4. Install the two wire terminals in the air compressor connector.
5. Install the wrap around four wires and secure with two harness ties.
6. Install four wires in the harness tie and install the harness tie on the air compressor head with the bolt. Tighten the bolt to 3 N.m (26 lb in).
7. Install the air dryer. Refer to «AUTOMATIC LEVEL CONTROL AIR DRYER REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
8. Install the heat shield and the harness tie on the air compressor bracket with the two bolts. Tighten the two bolts to 4 N.m (35 lb in).
9. Connect the air compressor connector to the connector anchor.
10. Install the air compressor on the vehicle. Refer to «AIR COMPRESSOR REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .

Air Tube Replacement

At the rear shock absorbers, the air tube connectors are held on with spring clips which snap into the grooves of the shock absorber air fittings. Air tube connectors are sealed using two O-rings.

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Note. Before disconnecting any air tube, clean the connector and the surrounding area to prevent dirt and other foreign material from entering the ELC system.

To disconnect an air tube from a shock absorber, rotate the spring clip 90 degrees out of the slots, and pull the connector from the shock absorber.

Note. Ensure that the air tube is routed correctly and all fasteners are used.

To connect an air tube to a shock absorber, lubricate the two O-rings using silicone lubricant, rotate the spring clip 90 degrees into the slots, and push the air tube connector on the shock absorber fitting until spring clip snaps into fitting groove.

1. Raise the vehicle.
2. Remove the air tube from the air dryer.
3. Remove the bolt and the harness tie from the air compressor bracket.
4. Remove both rear wheels. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels.
5. Disconnect the air tube from the left and right rear shock absorbers.
6. Remove the two metal clips from the air tube and the vehicle.
7. Remove the air tube with the three clips from the vehicle.

1. Connect the air tube to the air dryer. CAUTION: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the air tube with the harness tie and the bolt on the air compressor bracket.
3. Install the air tube on the vehicle with three clips.
4. Connect the air tube to the left and right rear shock absorbers.
5. Install two metal clips on the air tube and the vehicle. Place each clip immediately forward of the wheel house fold-over tabs on the LH and RH side of the vehicle.
6. Install both rear wheels. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels. NOTE: Before driving the vehicle, turn the ignition on and wait approximately 45 seconds. This will ensure that the air adjustable shock absorbers are filled with residual pressure.
7. Lower the vehicle.

1. Raise the vehicle.
2. Remove the right rear wheel. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels.
3. Remove the right rear fascia extension. Refer to «FASCIA EXTENSION REPLACEMENT - REAR»(/buick/lesabre/viii-2000-2005/remont/exterior-body-panels/#bumper-system) in Bumpers. NOTE: Before disconnecting the air hose from the intake air filter or the air compressor, clean the components and the surrounding area to prevent dirt and other foreign material from entering the ELC system.
4. Disconnect the air tube from the air dryer.
5. Remove the bolt and the harness tie with the air tube from the air compressor bracket.
6. Remove the intake air filter from the vehicle.
7. Remove the vehicle harness connector from the air compressor connector.
8. Remove the two nuts, the bolt, and the air compressor assembly from the vehicle.
9. Slide the air compressor connector off of the connector anchor.
10. Remove two bolts and the heat shield from the air compressor bracket.
11. Remove three bolts and the air compressor assembly from the bracket.
12. Remove the air dryer from the air compressor. Refer to «AUTOMATIC LEVEL CONTROL AIR DRYER REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
13. Remove the air hose from the air compressor at two places.
14. Remove the two screws and the two brackets from the air compressor.

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1. Install the two brackets on the air compressor with two screws. Tighten two screws to 7 N.m (62 lb in).
2. Connect the air hose to the air compressor at two places.
3. Install the air dryer on the air compressor. Refer to «AUTOMATIC LEVEL CONTROL AIR DRYER REPLACEMENT»(/buick/lesabre/viii-2000-2005/remont/electronic-suspension/#electronic-suspension-system-automatic-level-control) .
4. Install the air compressor assembly onto the bracket with three bolts. Tighten three bolts to 3 N.m (26 lb in). NOTE: Do not install the third heat shield bolt. It must be installed after the air tube is connected.
5. Install the heat shield on the air compressor bracket with two bolts. Tighten the two bolts to 4 N.m (35 lb in).
6. Install the air compressor connector to the connector anchor.
7. Install the air compressor assembly on the vehicle with two nuts and a bolt. Tighten the bolt to 9 N.m (80 lb in). Tighten the two nuts to 9 N.m (80 lb in).
8. Connect the harness connector to the air compressor connector.
9. Install the intake air filter on the vehicle.
10. Connect the air tube to the air dryer.
11. Connect the air tube and the harness tie to the air compressor bracket with the bolt. Tighten the bolt to 4 N.m (35 lb in).
12. Install the right rear fascia extension. Refer to «FASCIA EXTENSION REPLACEMENT - REAR»(/buick/lesabre/viii-2000-2005/remont/exterior-body-panels/#bumper-system) in Bumpers.
13. Install the right rear wheel. Refer to «TIRE & WHEEL REMOVAL & INSTALLATION»(/buick/lesabre/viii-2000-2005/remont/wheel-tire-system/#tires-wheels__tire-wheel-removal-installation) in Tires and Wheels. NOTE: Before driving the vehicle, turn the ignition on and wait approximately 45 seconds. This will ensure that the air adjustable shock absorbers are filled with residual pressure.
14. Lower the vehicle.

The Automatic Level Control (ALC) system automatically adjusts the rear height of the vehicle in response to changes in vehicle loading.

The ALC system consists of the Rear Integration Control Module (RIM), height sensor, an air compressor assembly, an ALC compressor relay, an intake hose and filter, an air tube, two rear shock absorbers. The air compressor assembly consists of an air compressor and an air dryer mounted on a bracket. The air compressor head is a replaceable part of the air compressor. The exhaust solenoid is a non-replaceable part of the air compressor head.

The compressor is activated when the ignition is on, and weight is added to the vehicle. The exhaust solenoid is connected directly to the battery (+), enabling the system to exhaust with the ignition on or off when excess weight is removed.

Raising Vehicle

When a load is added to the vehicle, the vehicle body moves down causing the sensor actuating arm to rotate upward. An arm movement of about 25 mm (1 in) amounts to a height change of about 12 mm I (1/2 in) at the rear bumper. The upward arm movement activates an internal timing circuit of the RIM module and, after an initial fixed delay of 17 to 27 seconds, the RIM module provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the struts through the air tubes.

As the struts inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1 in), the RIM module opens the compressor relay circuit, and the compressor is turned off.

Air Compressor Head Relief Sequence

In order to reduce current draw during air compressor starting, the RIM module performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows

1. Exhaust solenoid is energized.
2. Air compressor is activated 1.3 seconds after the exhaust solenoid is energized.
3. Exhaust solenoid is de-energized 0.5 seconds after the air compressor is activated.

Lowering Vehicle

When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit of the RIM module. After the initial fixed delay, the RIM module provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the struts, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1 in), the RIM module opens the exhaust solenoid circuit, which closes the exhaust solenoid valve and prevents air from escaping.

Air Replenishment Cycle

The sensor actuating arm position is checked when the ignition is turned on. If the sensor indicates that no height adjustment is needed, an internal timer circuit of the RIM module is activated. After about 35 to 55 seconds, the compressor is turned on for 3 to 5 seconds. This ensures that the struts are filled with the proper residual pressure. If weight is added to or removed from the vehicle during the time delay, the air replenishment cycle is overridden, and the vehicle rises or lowers after the normal delay.

Air Compressor Description

The air compressor is a positive displacement air pump, powered by a 12V DC permanent-magnet motor. The air compressor head contains intake and exhaust ports plus a solenoid-operated exhaust valve that releases air from the ALC system when energized. Air compressor intake air is drawn through an intake air hose and filter, mounted in the body rail. The air compressor is a serviceable part and is mounted on a bracket. The bracket is mounted to the underbody behind the right rear wheel well.

Air Dryer Description

The air dryer is attached to the air compressor head assembly at the pressure outlet and provides a dual function

1. It contains desiccant that absorbs moisture from the compressed air before it is delivered to the rear struts. Moisture is removed from the air dryer and returned to the atmosphere when air is exhausted out of the struts during lowering.
2. It contains valving that maintains a system residual pressure of 48-97 kPa (7-14 psi). This system pressure is maintained for improved ride characteristics and improved air sleeve reliability.

Exhaust Solenoid Description

The exhaust solenoid is a non-serviceable part of the air compressor head and provides a dual function

1. When energized, it exhausts air from the rear struts.
2. It acts as a relief valve to limit the maximum air pressure output of the compressor.

Automatic Level Control Sensor Description

The suspension position sensor is a potentiometer which detects height changes at the rear of the vehicle and, in turn, relays these changes to the RIM, which controls the functions of the compressor and exhaust solenoid. To prevent energizing the compressor relay or exhaust solenoid during normal ride motions, the RIM provides a calibrated delay before ground is completed to either circuit.

The sensor is mounted to the left rear side of the rear suspension support assembly. The actuation arm is attached to the left rear control arm by a short link.

Air Shock Absorber Or Strut Description

The rear air adjustable shock absorbers are constructed with a rubber-like air sleeve attached to the dust tube and reservoir. This sleeve forms a flexible chamber which extends the shock absorber when pressure in the chamber is increased. When air pressure is reduced, the weight of the vehicle collapses the shock absorber. In order to maintain proper operation and reliability of the air adjustable shock absorbers, a system pressure from 48-97 kPa (7-14 psi) must be maintained at all times.

Air Lines & Connectors Description

The air tube is a non-serviceable item consisting of the following

1. One connector at the ALC air dryer
2. Two tubes between the ALC air dryer and the two rear shock absorbers
3. Two connectors with spring clips, one at each rear shock absorber

At the rear shock absorbers, the air tube connectors are held on with spring clips which snap into the grooves of the shock absorber air fittings. Air tube connectors are sealed using 2 O-rings.

Although the tubes are flexible, care should be taken not to kink them and to keep them from contacting the exhaust system.

Scheme 27

See also:
• TESTING FOR INTERMITTENT & POOR CONNECTIONS
• TESTING FOR ELECTRICAL INTERMITTENTS
• CHECKING AFTERMARKET ACCESSORIES
• TIRE & WHEEL REMOVAL & INSTALLATION
• FASCIA EXTENSION REPLACEMENT - REAR
• DIAGNOSTIC SYSTEM CHECK - AUTOMATIC LEVEL CONTROL
• AIR COMPRESSOR LEAK TEST