height CHEVROLET DYNASTY 1993 User Guide

REAR LEVELING DIAGNOSTIC PROCEDURES
SELF-DIAGNOSTICS
A self-diagnostic procedure is available for the ser-
vice technician to use to detect system malfunctions.
BEFORE DIAGNOSTICS TEST
Check the 20 amp fuse (position W40) and the 30
amp circuit breaker (position W5) to be assured they
are functional components. Check all connectors that link the system into the
main body wiring harness. These include compressor,
height sensor, control module, (Fig. 7) and relay.
Also check the underbody to in trunk and leveling
harness to main body harness connectors. Also, check
all air lines, connectors, and other components for
correct installation.
TEST LAMP PIN OPERATION
The monitor lamp pin output will be activated (test
lamp on) if the detection of abnormal system opera-
tion is determined by the CM.
AFTER COMPLETION OF REPAIRS
To initiate diagnostics, disconnect the test ground
wire then reconnect for repair verification.
TERMINATION OF SELF-DIAGNOSTICS
The self-diagnostic operation is terminated when
any of the following takes place:
² Disconnecting the diagnostic input from the
ground circuit.
² Turn the ignition switch to the off position.
When the self-diagnostic operation is terminated.
The control module resumes normal operation unless
it ceases operation. Due to it detecting a system mal-
function.
TEST WEIGHT
Weight between 275-300 lbs. must be added to rear
of vehicle before diagnostic testing begins.
DIAGNOSTICS (TO START PROCESS)
(1) Remove protective connector cover from diag-
nostic connector. (2) Insert wire into diagnostic ground pin. Then at-
tach to compressor ground pin, or as an alternate, in-
sert wire into diagnostic ground pin. Then ground
other end of test wire to body structure or a control
module fastener.
IGNITION
The following self diagnostic operation is initiated
by connecting the diagnostic ground pin to ground af-
ter ignition switch is turned ON. A monitor lamp
must be connected between the Test Lamp Ground
Pin and the Test Lamp Feed Pin to display the con-
trol module diagnostics status. See (Fig. 8) for diag-
nostic test pin locations.
OPERATION
(1) The compressor relay output. From the control
module (CM), is activated until the vehicle is in the
high position. The maximum relay output operation
time is 150 610 seconds. If the expected position is
not obtained, the CM ceases self-diagnostics and any
further operation. (I.e. neither operates the compres-
sor relay or exhaust outputs). The monitor lamp out-
put is continuously activated until ignition is cycled
from OFF to ON or 60 61 minutes has elapsed after
ignition was turned off. See Diagnostics Chart 1. (2) The monitor lamp output should flash to indi-
cate the position of the height sensor. The sensor
should be in the high position. A continuously
lighted monitor lamp will indicate a system failure.
Such as the compressor relay output has operated for
150 610 seconds but the height sensor did not move
to the high position within the right shock absorber).
See Diagnostic Chart 1. (3) Next the exhaust solenoid output is activated
until the vehicle is in the low position. The maxi-
mum exhaust solenoid operation time is 120 610 sec-
onds. If the expected position is not obtained, the
module ceases self-diagnostics and any further oper-
ation. The monitor lamp output is lighted continu-
ously until ignition is cycled from OFF to ON or 60
6 1 minutes has elapsed after ignition is turned off.
See Diagnostic Chart 4. (4) The monitor lamp should flash to indicate the
height sensor is in the low position. A continuouslyFig. 7 Control Module Connector
Fig. 8 Diagnostic Test Pin Location
Ä SUSPENSION AND DRIVESHAFTS 2 - 65

lighted monitor lamp will indicate a system failure.
Such as the exhaust solenoid operated for 120 610
seconds but the height sensor did not move to the
low position. See Diagnostic Chart 4. (5) The compressor relay output is activated to re-
turn the vehicle to the neutral (leveled) position. The
maximum operation time of the relay output is 150
6 10 seconds. If the expected position is not obtained.
The control module ceases self-diagnostics and any
further operation. The monitor lamp is continuously
lighted until the ignition is cycled from OFF to ON
or 60 61 minutes has elapsed after ignition is turned
off. The sensor will move to the neutral position. If not,
a continuously lighted monitor lamp will indicate a system failure. Such as the compressor relay output
operated for 150 610 seconds but the sensor did not
move to or sense the neutral position. See Diagnostic
Chart 1. (6) Completion of diagnostics, is when self diagnostic
procedure is successfully completed and control module
resumes normal operation. The diagnostic test is now
complete. Throughout the testing the vehicle load must
be maintained at a specific level. No loads are allowed
to be added/removed to/from the vehicle once the self
diagnosis tests have been initiated. The Diagnostic connector cover must be in-
stalled after completion of the test.
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CONTROL MODULE
REMOVAL
(1) Disconnect negative battery cable.
(2) Remove right side trunk trim panel.
(3) Remove electrical connectors from control mod-
ule and relay (Fig. 9). (4) Remove control module mounting screws and
remove assembly.
INSTALLATION
(1) Install relay on the control module mounting
bracket (if required). (2) Place control module in mounting position.
(3) Install mounting screws and tighten to 2-3 N Im
(19-29 in. lbs.). (4) Install control module and relay wiring connec-
tors (Fig. 9). (5) Install right side trunk trim panel.
(6) Connect negative battery cable.
COMPRESSOR RELAY
REMOVAL
(1) Remove right side trunk trim panel.
(2) Remove electrical connector from relay.
(3) Remove relay from control module mounting
bracket by prying out on locating clip (Fig. 10).
INSTALLATION
(1) Push relay onto bracket (relay will Lock into
position). (2) Install electrical connector.
(3) Install trim panel.
RIGHT SHOCK ABSORBER (WITH HEIGHT
SENSOR)
REMOVAL
(1) Disconnect negative battery cable.
(2) Raise vehicle, see Hoisting, Group 0.
(3) Remove tire assembly.
(4) Disconnect height sensor connector, located on
right rear frame rail. (5) Remove both air lines connected to shock ab-
sorber ports. (6) Remove shock, see Shock Absorbers, Removal.
INSTALLATION
(1) Install shock assembly, see Shock Absorbers,
Installation. (2) Route height sensor wire through clip on shock
bracket, then tie strap to fuel filler tube. (3) Snap height sensor connector into underbody
harness connector. (4) Insert air lines.
(5) Install wheel/tire assembly.
Fig. 9 Control Module and Relay Wiring
Fig. 10 Control Module Connector
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AUTOMATIC AIR SUSPENSION INDEX
page page
Air Lines ............................... 75
Air Springs Rear ......................... 87
Compressor Performance Test .............. 77
Diagnosis .............................. 78
General Information ....................... 73
Recharge Air Spring ...................... 87 Right Shock Absorber (With Height Sensor)
.... 88
Safety Concerns ......................... 78
Service Procedures ....................... 85
Shipping Mode .......................... 78
Solenoids (Struts and Air Springs) ............ 86
System Operation ........................ 78
GENERAL INFORMATION
This system provides automatic height control and
low spring rates to improve suspension characteristics
of the vehicle. And it will automatically level the front
and rear of the vehicle. It will also maintain the opti-
mum vehicle attitude from one passenger through full
vehicle load.
The automatic air suspension system includes the
following components:
² Compressor/air dryer assembly
² Compressor relay
² Front struts
² Rear springs
² Rear shocks
² Control module
² Air lines ²
Compressor
² Rear height sensor
² Wiring harness assembly
² Compressor cover
Front springs (and height sensors) are integral with
the shock absorber strut assemblies. While rear air
springs replace conventional steel units. Rear height is
controlled via a height sensor contained within the
right rear shock absorber. Solenoids (integral with each
air spring) control air volume/pressure requirements.
Pressurized air is distributed from the air compressor/
dryer assembly and routed to each air spring by four
separate air lines. The air lines start at the dryer and
terminate at the individual air springs. The system is
monitored and controlled by the Air Suspension Control
Module (ASCM) (Fig. 1).
Fig. 1 Automatic Air Suspension
Ä SUSPENSION AND DRIVESHAFTS 2 - 73

FRONT AND REAR AIR SPRINGS
The front and rear air springs are essentially pneu-
matic cylinders that replace the steel coil springs.
The air filled springs allow the vehicle suspension
height to be adjusted for all weight conditions. The air springs allow for the reduction of spring
rates to improve vehicle ride characteristics.
FRONT/REAR SPRING SOLENOIDS
The front and rear solenoids control air flow in and
out of the front and rear springs. The Air Suspension
Control Module (ASCM) opens the solenoids when
the system requires air to be added to or exhausted
from the air springs. The solenoids operate at a cur-
rent draw range of 0.6 to 1.5 amps.
HEIGHT SENSOR
A magnetic switch type sensor. Located in the
right rear shock absorber and left and right front
struts, (Fig. 2) monitors vehicle height. The sensors
transmit signals to the (ASCM) relating to vehicle
height status (low, trim, medium, high).
CONTROL MODULE
The Air Suspension Control Module (ASCM). Is a
device that controls the ground circuits for the Com-
pressor Relay, Compressor Exhaust Solenoid Valve
and Front and Rear Solenoid Valves. The (ASCM)
limits the compressor pump operation time to 170 to
190 seconds. This controlled operation time is to pre- vent damage to the compressor motor.
To prevent excessive cycling between the compres-
sor and the exhaust solenoid circuits during normal
ride conditions. A 14 to 16 second delay is incorpo-
rated in the microprocessor logic. The system is non-operation when one of the fol-
lowing conditions exists. A door(s) is/are open, the
trunk is open, the service brake is applied or the
throttle position sensor is 65% to 100% open. System
operation is inhibited during high speed cornering
activities or if there is a charging system failure.
The control module is on the CCD bus system.
COMPRESSOR ASSEMBLY
The compressor assembly is driven by an electric
motor and supplies air pressure between 930 to 1241
kPa (135 to 180 psi) (Fig. 3). A solenoid operated ex-
haust valve. Located in the compressor head assem-
bly, releases air when energized. A heat actuated circuit breaker. Located inside the
compressor motor housing. Is used to prevent damage
to the compressor motor in case of control module
failure.
COMPRESSOR AIR DRYER
The air dryer is attached to the compressor (Fig. 3).
This component serves two purposes. It absorbs mois-
ture from the atmosphere before it enters the system
Fig. 2 Front and Rear Air Springs
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Fig. 5 Air Lines Rear, and Rear Height Sensor
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(3) Check solenoid to volume canister joint.
² Front strut to solenoid valve connection.
² Rear spring to solenoid valve connection.
(4) Check air line for ruptures, cuts, splits or heat
damage. Use a soap and water solution or a liquid de-
veloped for leak detection.
SYSTEM OPERATION
ENGINE RUN OPERATION
The system will compensate for load
addition/removal when.
² The trunk and all doors are closed.
² The engine speed exceeds 600 R.P.M.
² Throttle angle is less than 65 degrees.
² The brake is not applied.
² You are not cornering above 10 mph.
² There is not a charging system problem with the
vehicle.
ENGINE OFF OPERATION
After passengers/load is removed from the vehicle
the system will correct the vehicle attitude after:
² The trunk and all doors are closed.
² The ignition switch is in the OFF position.
Opening the a door or trunk wakes up the body
computer and the air suspension module. The air
suspension system is now capable of leveling, if
required.
LONG TERM IGNITION OFF OPERATION
The system is capable of one an additional leveling
cycle. After 2 continuous hours of ignition key off and
no door open or trunk open activities. This feature is
implemented to eliminate possible ice freeze-up be-
tween the tire and the inner fender shield.
SYSTEM OPERATION INHIBITORS
The air suspension system is inhibited when:
² The trunk is open.
² A door(s) is/are open.
² The brake pedal is engaged.
² The throttle is at the wide open position.
² The charging system fails.
The maximum compressor pump or exhaust
time is 3 minutes.
SYSTEM FAILURES
Vehicles equipped with air suspension and overhead
console. Will alert the driver of an air suspension
system malfunction. A warning Check Air Suspension
will appear on the overhead console screen.
SAFETY CONCERNS
WARNING: REAR AIR SPRINGS MUST BE DEFLATED
BEFORE BEING REMOVED FROM THE VEHICLE.
WARNING: OPEN TRUNK, OR DOOR(S) OR REMOVE
GROUND STRAP FROM BATTERY BEFORE HOIST-
ING OR JACKING A VEHICLE DURING MECHANICAL
REPAIRS.
WARNING: IF THE VEHICLE NEEDS SERVICE OR
REPAIR OF THE REAR SHOCK ABSORBERS OR
REAR AXLE PIVOT BUSHINGS. THE REAR AIR
SPRINGS MUST HAVE THE AIR PRESSURE RE-
MOVED BEFORE THE VEHICLE CAN BE SERVICED
SAFELY.
SHIPPING MODE
(1) Removing shipping height signal for customer
use.
² Use DRB II tester and 1991 Chassis (Air Suspen-
sion) service cartridge.
² Follow DRB II requirements to cancel shipping
height message in the body computer.
² Connect the Ignition Off Draw (I.O.D.) circuit.
The connection of the IOD circuit will cancel
the Shipping height signal. (2) Return to shipping height.
² Set shipping command in the body computer using
the DRB II and the 1991 Chassis (Air suspension)
service cartridge.
² Disconnect the I.O.D. connector.
DIAGNOSIS
INITIAL DIAGNOSTIC CHECK
(1) Check for blown or missing fuses.
Fig. 9 Compressor Current Draw Test
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(2) Check all connectors for correct assembly. Check
all connectors for incorrectly installed termi-
nals. (3) Check pin #21 for minimum of 9.5 volts.
(4) Check pin #20 for minimum of 9.5 volts (with
ignition key on). (5) Check voltage at pins #5 and #16. The measure-
ment should exceed 0 volts. (6) Check pin #19 for continuity.
(7) The engine speed should exceed 680 rpm during
idle. All doors and trunk must be closed for the
system to function.
DIAGNOSTICS PROCEDURES
(1) Use the D.R.B. II tester and the 1991 air suspen-
sion diagnostic service cartridge to begin the trouble-
shooting process. (2) Use the D.R.B. mating connector under the dash
(drivers side) to plug-in the D.R.B. II test connector
(Fig. 10). (3) The tester will conduct a complete check of the
suspension system status. (4) The tester will list the steps to follow to access
and diagnose the failure. (5) A Volt/Ohm meter can be used for some diagnos-
tic testing.
HEIGHT SENSOR CHECK
If a sensor signal/signals are missing. Follow the
repair procedure listed below. (1) Check ground circuit continuity. (Remember
front and rear grounds are on different circuits. (2) For front ground circuit continuity check circuit
S 33. (3) For rear ground circuit continuity check circuit
X20. (4) Refer to control module pin out chart and wiring
diagram (see Group 8F in wiring diagram manual) for
individual circuit details. (5) If open circuits are not found replace the compo-
nent. Complete circuit testing and connector assem-
blies before replacing a strut or right rear shock. (6) To measure resistance values, see Height Sensor
Logic Chart and Initial Diagnostic Check in System
Operation.
HEIGHT SENSOR LOGIC CHART
Ä SUSPENSION AND DRIVESHAFTS 2 - 79

INSTALL
(1) Inspect O-Ring condition and position on sole-
noid stem. (O-Ring can become dislodged during re-
moval (Fig. 16). (2) Install solenoid with tangs to top ledge of hous-
ing and install retaining clip. (3) Reconnect air line and electrical connection.
STRUT (AIR SUSPENSION) DAMPERASSEMBLY
Service procedures for removal and installation for
(air or steel spring) assemblies are essentially the
same. Except for air venting/recharging and discon-
necting/connecting air lines and electrical connection.
REMOVAL (1) Disconnect battery negative cable.
(2) Hoist vehicle and remove wheel and tire assem-
bly. (3) See AIR LINES AND FITTINGS and discon-
nect air line. (4) Disconnect electrical leads, solenoid and height
sensors. (5) See SOLENOIDS (STRUT AND AIR SPRING)
and vent air spring and remove solenoids. (6) See STRUT DAMPER ASSEMBLY in FRONT
SUSPENSION and remove strut.
DISASSEMBLY/ASSEMBLE Disassembly is restricted to upper mount and bear-
ing housing. The strut shock absorber, air spring
with integral height sensor, solenoid and wiring har-
ness are serviced as an assembly. (1) Hold retaining plate locking washer and re-
move strut rod nut. (2) Remove locking washer, retainer plate, spacer,
flat washer and mount/bearing housing assembly
(Fig. 17). (3) Assemble in reverse order. Hold retainer plate
locking washer with suitable tool and tighten strut
rod nut to 75 N Im (55 ft. lbs.) torque.
INSTALLATION (1) See STRUT DAMPER ASSEMBLY in FRONT
SUSPENSION and install strut. (2) Install solenoid, see: SOLENOIDS (STRUT
AND AIR SPRINGS). (3) Connect electrical leads, solenoid and height
sensor. (4) Charge (inflate) air spring. See RECHARGE-
AIR SPRING to activate spring solenoid and air com-
pressor. Add air for 60 seconds.
RECHARGE AIR SPRING
To activate compressor; Ground Pin S08 to Pin
X20. To Activate Spring Solenoid:
² LF: Ground Pin S31 to X20 ²
RF: Ground Pin S30 to X20
² RR: Ground Pin S32 to X20
AIR SPRINGS REAR
REMOVAL
(1) Disconnect battery negative cable, hoist vehicle
and remove wheel and tire assembly. (2) See AIR LINES AND FITTINGS and discon-
nect air line and electrical connector from solenoid. (3) See SOLENOIDS (STRUT AND AIR SPRINGS)
and vent air from spring. Remove solenoid. (4) Release upper air spring alignment/retainer
clips. (Fig. 18) (5) Remove lower spring to axle nut (Fig. 19).
(6) Pry assembly down to pull alignment studs
through retaining clips (Fig. 20). Remove assembly.
INSTALLATION
(1) Position assembly lower stud into axle seat and
upper alignment pins through frame rail adaptor. (2) Install upper retaining clips.
(3) Install lower spring to axle nut: LOOSE AS-
SEMBLE. (4) Install solenoid and connect air line and electri-
cal connector. (5) Charge (inflate) air spring. See RECHARGING
AIR SPRING and add air for 60 seconds. (6) AFTER partial air recharge tighten lower nut
Fig. 17 Air Strut Upper Mount Assembly
Ä SUSPENSION AND DRIVESHAFTS 2 - 87

to 68 N Im (50 ft. lbs.) torque.
(7) Install wheel and tire assembly. Lower vehicle,
install wheel and tire assembly and connect battery
negative cable.
RIGHT SHOCK ABSORBER (WITH HEIGHT
SENSOR)
REMOVAL
(1) Disconnect battery negative cable.
(2) Raise vehicle, see Hoisting, Group 0.
(3) Remove tire assembly.
(4) Disconnect height sensor connector located on
right rear frame rail. (5) Remove shock, see Shock Absorbers, Removal.
INSTALLATION
(1) Install shock assembly, see Shock Absorbers,
Installation. (2) Route height sensor wire through retaining
clips and then tie strap to fuel filler tube. (3) Snap height sensor connector into underbody
harness connector. (4) Install wheel/tire assembly.
(5) Height sensor wiring harness and white paint
mark on bottom shock eye must face to the front of
the vehicle (Fig. 21).
Fig. 18 Release Retaining Clips
Fig. 19 Remove/Install Lower Spring to Axle Nut
Fig. 20 Pry Assembly Out of Retaining Clips
Fig. 21 Right Rear Shock Absorber Installation
2 - 88 SUSPENSION AND DRIVESHAFTS Ä