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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
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AUTOMATIC AIR LOAD LEVELING DIAGNOSTICS
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AUTOMATIC AIR LOAD LEVELING DIAGNOSTICS
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AUTOMATIC AIR LOAD LEVELING DIAGNOSTICS
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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