air suspension INFINITI QX56 2008 Factory Workshop Manual

CONTROL UNITRSU-25
< REMOVAL AND INSTALLATION >
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CONTROL UNIT
Removal and InstallationINFOID:0000000004900764
REMOVAL
1. Remove the rear LH interior trim panel. Refer to INT-14, "Removal and Installation" .
2. Disconnect the battery negative terminal.
3. Disconnect the suspension control unit electrical connector.
4. Remove the two bolts and remove the suspension control unit.
INSTALLATION
Installation is in the reverse order of removal.
Initialization ProcedureINFOID:0000000004900765
1. If control unit has been replaced, proceed to step 2. If control unit has not been replaced, use CONSULT-
III “CLEAR HEIGHT INI” work support function to cl ear initialization flag and value. The CK SUSP warning
lamp should illuminate. Using CONSULT-III “EXHAUST SOLENOID” active test, release the air pressure
from the rear load leveling air suspension system.
2. Roll vehicle forward and backward.
3. Use CONSULT-III “ADJUST HEIGHT INI” work support function to set initialization condition.
4. Confirm that CK SUSP warning lamp is OFF.
LEIA0100E
Suspension control unit bolt s : 6 N·m (0.6 kg-m, 53 in-lb)
Revision: March 2010 2008 QX56

RSU-26
< REMOVAL AND INSTALLATION >
HEIGHT SENSOR
HEIGHT SENSOR
Removal and InstallationINFOID:0000000004900766
Rear Load Leveling Air Suspension System
REMOVAL
1. Use CONSULT-III “EXHAUST SOLENOID” active test to release the air pressure from the rear load level-
ing air suspension system.
2. Disconnect the electrical connector for the height sensor.
3. Remove the two height sensor bolts and height sensor arm bracket bolt.
4. Remove the height sensor.
INSTALLATION
Installation is in the reverse order of removal.
AWEIA0054GB
1. Rear load leveling air suspension hose, RH 2. Shock absorber, RH
3. Height sensor
4. Rear load leveling air suspension hose, LH 5. Shock absorber, LH
6. Rear load leveling air suspension
compressor assembly
Front
LEIA0080E
Revision: March 2010 2008 QX56

SERVICE DATA AND SPECIFICATIONS (SDS)RSU-29
< SERVICE DATA AND SPECIFICATIONS (SDS)
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Wheelarch Height (Unladen*1)INFOID:0000000004918900
Unit: mm (in)
*1: Fuel, engine coolant and engine oil full. Spare tire, jack, hand tools and mats in designated positions.
*2: Verify the vehicle height. If vehicle height is not within ± 10 mm (0.39 in) of the specification, perform the control unit initialization pro-
cedure. Refer to SCS-7, "
CONSULT-III Function" .
Suspension type
Air leveling*
2
Applied model2WD 4WD
Front wheelarch height (Hf) 920
(36.22) 937
(36.89)
Rear wheelarch height (Hr) 917
(36.10) 937
(36.89)
LEIA0085E
Revision: March 2010 2008 QX56

SCS-1
SUSPENSION
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SECTION SCS
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SUSPENSION CONTROL SYSTEM
BASIC INSPECTION ....... .............................3
DIAGNOSIS AND REPAIR WORKFLOW ..... .....3
Work Flow ........................................................... ......3
FUNCTION DIAGNOSIS ...............................5
SUSPENSION CONTROL SYSTEM .............. .....5
System Diagram .................................................. ......5
System Description ...................................................5
Component Parts Location ........................................6
Component Description .............................................6
DIAGNOSIS SYSTEM (SUSPENSION CON-
TROL UNIT) .........................................................
7
CONSULT-III Function ..............................................7
COMPONENT DIAGNOSIS ..........................9
C1801 VEHICLE HEIGHT SENSOR .............. .....9
Description .......................................................... ......9
DTC Logic .................................................................9
Diagnosis Procedure ................................................9
C1802 COMPRESSOR RELAY .........................10
Description ..............................................................10
DTC Logic ...............................................................10
Diagnosis Procedure ..............................................10
C1803 EXHAUST SOLENOID ...........................11
Description ..............................................................11
DTC Logic ...............................................................11
Diagnosis Procedure ..............................................11
C1804 HEIGHT ADJUSTING MALFUNCTION
(COMPRESSOR) ............................................ ....
12
Description .......................................................... ....12
DTC Logic ...............................................................12
Diagnosis Procedure ..............................................12
C1805 HEIGHT ADJUSTING MALFUNCTION
(EXH SOLENOID) ..............................................
13
Description ........................................................... ....13
DTC Logic ................................................................13
Diagnosis Procedure ..............................................13
C1806 VEHICLE HEIGHT SENSOR LOCK-
ING MALFUNCTION .........................................
14
Description ........................................................... ....14
DTC Logic ................................................................14
Diagnosis Procedure ...............................................14
C1807 SENSOR 5V MALFUNCTION ...............15
Description ...............................................................15
DTC Logic ................................................................15
Diagnosis Procedure ..............................................15
C1808 INTEGRAL TIME MALFUNCTION
SUPPLYING AIR ...............................................
16
Description ...............................................................16
DTC Logic ................................................................16
Diagnosis Procedure ..............................................16
POWER SUPPLY AND GROUND CIRCUIT ....17
SUSPENSION CONTROL UNIT ................................17
SUSPENSION CONTROL UNI T : Diagnosis Pro-
cedure .................................................................. ....
17
SUSPENSION AIR COMPRESSOR ..........................17
SUSPENSION AIR COMPRESSOR : Diagnosis
Procedure ............................................................ ....
17
HEIGHT SENSOR .................................................. ....18
HEIGHT SENSOR : Diagnosis Procedure ..............18
COMPRESSOR MOTOR RELAY .....................20
Description ...............................................................20
Component Function Check ....................................20
Diagnosis Procedure ...............................................20
HEIGHT SENSOR SIGNAL CIRCUIT ...............22
Description ...............................................................22
Component Function Check ....................................22
Diagnosis Procedure ...............................................22
Revision: March 2010 2008 QX56

SCS-2
EXHAUST VALVE SOLENOID CIRCUIT ..........23
Description ........................................................... ...23
Component Function Check ...................................23
Diagnosis Procedure ..............................................23
CK SUSP WARNING INDICATOR CONTROL
CIRCUIT .............................................................
25
Description ........................................................... ...25
Component Function Check ...................................25
Diagnosis Procedure ..............................................25
ECU DIAGNOSIS ..................................... ...27
SUSPENSION CONTROL UNIT ........................27
Reference Value .................................................. ...27
Wiring Diagram .......................................................28
DTC Index ..............................................................33
SYMPTOM DIAGNOSIS .............................35
SUSPENSION CONTROL SYSTEM .............. ...35
Symptom Table ................................................... ...35
SUSPENSION CONTROL SYSTEM INOPER-
ATIVE .................................................................
36
Description ........................................................... ...36
Diagnosis Procedure ...............................................36
SUSPENSION CONTROL SYSTEM DOES
NOT RAISE ........................................................
37
Description ........................................................... ...37
Diagnosis Procedure ...............................................37
SUSPENSION CONTROL SYSTEM DOES
NOT LOWER .....................................................
38
Description ........................................................... ...38
Diagnosis Procedure ...............................................38
PRECAUTION ............................................39
PRECAUTIONS .............................................. ...39
Precaution for Supplemental Restraint System
(SRS) "AIR BAG" and "SEAT BELT PRE-TEN-
SIONER" .............................................................. ...
39
Precaution for Rear Suspension .............................39
Revision: March 2010 2008 QX56

SUSPENSION CONTROL SYSTEMSCS-5
< FUNCTION DIAGNOSIS >
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FUNCTION DIAGNOSIS
SUSPENSION CONTROL SYSTEM
System DiagramINFOID:0000000001731955
System DescriptionINFOID:0000000001731956
SUSPENSION CONTROL SYSTEM
The suspension control system consists of the following components
• Suspension control unit
• Compressor motor relay
• Suspension air compressor
• Exhaust valve solenoid (built into suspension air compressor)
• Height sensor
The suspension control unit monitors vehicle ride height as indicated by the height sensor. The suspension
control unit actuates the compressor motor relay to ra ise the vehicle ride height. The suspension control unit
actuates the exhaust valve solenoid to lower the vehicle ride height.
CK SUSP INDICATOR LAMP
The CK SUSP indicator lamp ground is controlled by the suspension control unit. The indicator lamp will come
on for 2 seconds when the ignition switch is turned ON. If the indicator lamp does not turn OFF there is a fault
detected. Refer to SCS-7, "
CONSULT-III Function"
ALEIA0042GB
Revision: March 2010 2008 QX56

SCS-6
< FUNCTION DIAGNOSIS >
SUSPENSION CONTROL SYSTEM
Component Parts Location
INFOID:0000000001731957
:Front
Component DescriptionINFOID:0000000001731958
1. Suspension control unit B3 (view with upper and lower luggage side finishers
LH removed) 2. Suspension air compressor C9 (view
under vehicle behind LH rear suspen-
sion) 3. Height sensor C8 (view under vehicle
at LH rear suspension)
4. Compressor motor relay E130, E131 (view with battery removed)
ALEIA0044ZZ
Part name Description
Suspension control unit • Monitors height sensor input to determine vehicle height.
• Actuates the compressor motor relay or exhaust valve solenoid to raise or
lower the vehicle accordingly.
• Sends a ground signal to the combination meter to activate the CK SUSP indicator lamp.
Suspension air compressor (with built in exhaust valve
solenoid) • When the compressor is actuated, it pumps air into the system to raise the
rear suspension.
• When the exhaust valve solenoid is actuated, it vents air from the system to lower the rear suspension.
Height sensor Provides vehicle height input to the suspension control unit.
Revision: March 2010 2008 QX56

DIAGNOSIS SYSTEM (SUSPENSION CONTROL UNIT)
SCS-7
< FUNCTION DIAGNOSIS >
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DIAGNOSIS SYSTEM (SUS PENSION CONTROL UNIT)
CONSULT-III FunctionINFOID:0000000001731959
CONSULT-III can display each diagnostic item using the diagnostic test modes shown following.
WORK SUPPORT
Display Item List
SELF-DIAG RESULTS
Display Item List
Refer to SCS-33, "DTC Index".
DATA MONITOR
Display Item List
ACTIVE TEST
CAUTION:
Do not perform active test while driving.
Display Item List
AIR LEVELIZER diagno sis mode Description
WORK SUPPORT Supports inspection and adjustment. Commands are transmitted to the suspension control
unit for setting the status suitable for required operation, input/output signals are received
from the suspension control unit and received data is displayed.
SELF-DIAG RESULTS Displays suspension control unit self-diagnosis results.
DATA MONITOR Displays suspension control unit input/output data in real time.
ACTIVE TEST Operation of electrical loads can be checked by sending drive signal to them.
ECU PART NUMBER The part number of suspension control unit can be checked.
ItemDescription Condition
STANDARD HEIGHT LEVEL Resets the vehicle height to the initialization flag
setting stored in the suspension control unit. Vehicle unladen, set in a horizontal position and
not moving.
NOTE:
Do not take your eyes off the vehicle while CON-
SULT-III is processing.
ADJUST HEIGHT INI Sets the height initialization flag in the suspen-
sion control unit when the control unit has been
replaced or when the initialization flag has been
cleared using the "CLEAR HEIGHT INI" proce-
dure. Vehicle unladen, move vehicle forward and back-
ward approx. 5 m (16.4 ft) and rock vehicle side
to side.
NOTE:
Do not move vehicle wh
ile CONSULT-III is pro-
cessing.
CLEAR HEIGHT INI Clears the initialization flag in the suspension
control unit. Vehicle unladen.
Display item [unit]
ALL
SIGNALS SELECTION FROM MENU
HEIGT SEN [V] XX
HEIGT CALC [mm] XX
SEN FIX TIME [HR] XX
HEIGT INI VAL [V] XX
COMPRESSOR [ON/OFF] XX
EXH SOLENOID [ON/OFF] XX
ACG L [ON/OFF] XX
Revision: March 2010 2008 QX56

C1801 VEHICLE HEIGHT SENSORSCS-9
< COMPONENT DIAGNOSIS >
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COMPONENT DIAGNOSIS
C1801 VEHICLE HEIGHT SENSOR
DescriptionINFOID:0000000001731960
The vehicle height sensor operates on a 5 volt referenc e signal from the suspension control unit. The suspen-
sion control unit also provides ground to the height sensor. Depending on vehicle height, the height sensor
signal should have between 0.2V and 4.8V.
DTC LogicINFOID:0000000001731961
DTC DETECTION LOGIC
Diagnosis ProcedureINFOID:0000000001731962
1.CHECK HEIGHT SENSOR OPERATION
CONSULT-III
1. Turn ignition switch ON
2. Select "HEIGT SEN" of AIR L EVELIZER data monitor test item.
Is the HEIGHT SEN voltage within the given range?
YES >> Height sensor is operating normally.
NO >> Refer to SCS-22, "
Diagnosis Procedure".
DTCDisplay contents of CON-
SULT-III Diagnostic item is detected when ...
Probable malfunction location
C1801 VEHICLE HEIGHT SEN-
SOR Vehicle height sensor voltage is less than 0.2V
or greater than 4.8V for more than 60 seconds. • Height sensor power/ground supply. Refer to
SCS-18, "
HEIGHT SENSOR : Diagnosis
Procedure"
• Height sensor signal circuit. Refer to SCS-
22, "Component Function Check"
HEIGHT SEN : 0.2V - 4.8V
Revision: March 2010 2008 QX56

SCS-10
< COMPONENT DIAGNOSIS >
C1802 COMPRESSOR RELAY
C1802 COMPRESSOR RELAY
DescriptionINFOID:0000000001731963
The compressor motor relay is controlled by the suspension control unit. The suspension control unit supplies
voltage to the coil side of the relay to activate it. T he compressor motor relay, when activated, supplies power
to the suspension air compressor.
DTC LogicINFOID:0000000001731964
DTC DETECTION LOGIC
Diagnosis ProcedureINFOID:0000000001731965
1.CHECK COMPRESSOR MOTOR RELAY OPERATION
CAUTION:
The "COMPRESSOR" active test will remain ON until it is turned off using CONSULT-III. Allowing the
compressor to run for an extended period of time may cause damage to the air levelizer system com-
ponents due to excessive air pressure.
CONSULT-III
1. Turn ignition ON.
2. Select "COMPRESSOR" of AIR LEVELIZER active test items.
3. While operating test item, check that the suspension air compressor turns ON.
Does the suspension air compressor operate properly?
YES >> Compressor motor relay and suspension air compressor are operating normally.
NO >> Refer to SCS-20, "
Diagnosis Procedure"
DTCDisplay contents of CON-
SULT-III Diagnostic item is detected when ...
Probable malfunction location
C1802 COMPRESSOR RELAY • Driving transistor for the compressor
relay is
OFF and monitor voltage continues at a high
level for more than 10 seconds.
• Driving transistor for the compressor relay is
ON and monitor voltage continues at a low
level for more than 5 seconds. Compressor motor relay. Refer to
SCS-20,
"Component Function Check"
ON : Compressor turns ON
OFF : Compressor turns OFF
Revision: March 2010 2008 QX56