2011 INFINITI QX56 ABS

DESCRIPTIONSCS-49
< SYSTEM DESCRIPTION > [AIR LEVELIZER CONTROL SYSTEM]
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SYSTEM DESCRIPTION
DESCRIPTION
DescriptionINFOID:0000000006256039
 Corrects sinkage of vehicle rear that occurs in laden or towing conditions.
 Maintains vehicle height at a constant level and improv es riding comfort by charging or discharging air in air
chamber of rear shock absorber, according to signal from vehicle height sensor installed to rear suspension.
Revision: 2010 May2011 QX56

SCS-50
< SYSTEM DESCRIPTION >[AIR LEVELIZER CONTROL SYSTEM]
COMPONENT PARTS
COMPONENT PARTS
Component Parts LocationINFOID:0000000006256040
Component DescriptionINFOID:0000000006256041
1. Combination meter
Refer to MWI-6, "
METER SYSTEM
: Component Parts Location".2. CK SUSP indicator lamp 3. Air levelizer control module
4. Air compressor relay 5. Air chamber 6. Air compressor
7. Vehicle height sensor
A. Inside of luggage side finisher low- er (LH) B. Engine room (RH) C. Rear shock absorber
D. Vehicle rear (LH)
JSEIA0223GB
Component parts Reference
Air levelizer control module SCS-51, "
Air Levelizer Control Module"
Vehicle height sensorSCS-51, "Vehicle Height Sensor"
Air compressor
SCS-51, "Air Compressor"Exhaust solenoid
Revision: 2010 May2011 QX56

COMPONENT PARTSSCS-51
< SYSTEM DESCRIPTION > [AIR LEVELIZER CONTROL SYSTEM]
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Air Levelizer Control ModuleINFOID:0000000006256042
 Operates ON/OFF of air compressor (exhaust solenoid) , according to signal from vehicle height sensor.
 Transmits CK SUSP indicator lamp signal to the combination meter via CAN communication, when setting of standard vehicle height is incomplete.
 If malfunction is detected, the syste m enters fail-safe mode. Refer to SCS-59, "
Fail-safe".
Vehicle Height SensorINFOID:0000000006256043
Measures vehicle height of vehicle rear and transmits th is information to air levelizer control module according
to electric signal.
Air CompressorINFOID:0000000006256044
Operates according to signal from air levelizer control module via air compressor relay, and charges air in air
chamber of rear shock absorber.
EXHAUST SOLENOID
Operates according to signal from air levelizer control module, and discharges air in air chamber of rear shock
absorber.
Air Compressor RelayINFOID:0000000006256045
Turns ON according to signal from air levelizer control module, and operates air compressor.
CK SUSP Indicator LampINFOID:0000000006256046
 Turns ON for 2 seconds when ignition switch is turned ON, for the purpose of bulb check.
 Turns ON when setting of standard vehicle height is incomplete.
NOTE:
Does not turn ON when the system is malfunctioning.
Air compressor relay SCS-51, "Air Compressor Relay"
CK SUSP indicator lampSCS-51, "CK SUSP Indicator Lamp"
Component parts Reference
Revision: 2010 May2011 QX56

SCS-52
< SYSTEM DESCRIPTION >[AIR LEVELIZER CONTROL SYSTEM]
STRUCTURE AND OPERATION
STRUCTURE AND OPERATION
Rear Shock AbsorberINFOID:0000000006256047
 Discharges air in air chamber (2) from air valve (1)
when vehicle height of vehicle rear is higher than stan-
dard vehicle height, has shock absorber stroke in compressed direction, lowers vehicle height, and returns it
to standard vehicle height.
 Also charges air in air chamber from air valve when height of vehicle rear is lower than standard vehicle
height, has shock absorber stroke in extending directi on, raises vehicle height, and returns it to standard
vehicle height.
 Charged air, because of rubber (3) that is hard and loca ted on side surface, does not expand in lateral direc-
tion, but expands in vertical direction, and enables shock absorber to extend or retract.
Without Hydraulic Body-Motion Control System
With Hydraulic Body-M otion Control System
JSEIA0217ZZ
1. Air valve 2. Air chamber 3. Rubber
A. Stroke
: Vehicle upper
JSEIA0218ZZ
1. Air valve 2. Air chamber 3. Rubber
A. Stroke
: Vehicle upper
Revision: 2010 May2011 QX56

SCS-54
< SYSTEM DESCRIPTION >[AIR LEVELIZER CONTROL SYSTEM]
SYSTEM
SYSTEM
System DiagramINFOID:0000000006256049
System DescriptionINFOID:0000000006256050
 Based on the signal from the vehicle height sensor, t
he air levelizer control module operates the air com-
pressor (exhaust solenoid) and controls vehicle height so that it remains at a constant height. This operation
occurs if vehicle height of vehicle rear is judged to be 15 mm (0.59 in) or more or 15 mm (0.59 in) or less
than standard vehicle height, continuously for 30 seconds, when engine is started.
 If malfunction is detected, the system enters fail-safe mode. Refer to SCS-59, "
Fail-safe".
INPUT/OUTPUT SIGNAL
Air levelizer control module transmits and receives following signals between each control unit via CAN com-
munication line.
OPERATING PRINCIPLE
System Time Table
JSEIA0220GB
Component parts Control signal
ECM Transmits the following signal via CAN communication line to air levelizer control module.
 Engine speed signal
Combination meter Receives the following signal via CAN communication line from air levelizer control module.
 CK SUSP indicato
r lamp signal
ABS actuator and elec tric unit (con-
trol unit) Transmits the following signal via CAN communication line to air levelizer control module.
 Vehicle speed signal
Revision: 2010 May2011 QX56

SYSTEMSCS-55
< SYSTEM DESCRIPTION > [AIR LEVELIZER CONTROL SYSTEM]
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Vehicle height raises [When starting engi
ne, if vehicle height of vehicle rear continues for 30 seconds or more in a
status that is 15 mm (0.59 in) or less than standard vehicle height]
1. Vehicle height sensor detects vehicle height status, and transmits this information to air levelizer control
module.
2. Air levelizer control module turns air compressor relay ON and operates air compressor.
3. Air compressor charges air in air chamber of shock absorber.
4. Vehicle height raises, and control is complete when status is −1 mm ( −0.04 in) of standard vehicle height
value.
Vehicle height lowers [When starting engine, if vehicle height of vehicle rear continues for 30 seconds or more in a
status that is 15 mm (0.59 in) or more of standard vehicle height]
1. Vehicle height sensor detects vehicle height status, and transmits this information to air levelizer control
module.
2. Air levelizer control module turns exhaust solenoid of air compressor ON.
3. Air compressor discharges air from air chamber of shock absorber.
4. Vehicle height lowers, and control is complete when st atus is +1 mm (+0.04 in) of standard vehicle height.
Fail-safeINFOID:0000000006256051
If malfunction is detected, control stops.
The system may enter fail-safe mode under certain conditions (for example, over-laden conditions) when elec-
tronic circuit is normal.
In this case, always check that the system re turns to normal by starting engine after unloading load.
JSEIA0221GB
Revision: 2010 May2011 QX56

C1804 VHCL HEIGHT ADJ UPSCS-77
< DTC/CIRCUIT DIAGNOSIS > [AIR LEVELIZER CONTROL SYSTEM]
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C1804 VHCL HEIGHT ADJ UP
DTC LogicINFOID:0000000006256070
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.PRECONDITIONING
If “DTC CONFIRMATION PROCEDURE” has been previous ly conducted, always turn ignition switch OFF
andwait at least 10 seconds before conducting the next test.
>> GO TO 2.
2.CHECK DTC DETECTION
With CONSULT-III
1. Set vehicle in the unloaded vehicle status.
2. Start the engine and wait 150 seconds or more.
3. Perform “Self Diagnostic Result” in “E-SUS”.
Is
“C1804” detected ?
YES >> Go to SCS-77, "DiagnosisProcedure".
NO >> INSPECTION END
Diagnosis ProcedureINFOID:0000000006256071
1.CHECK APPEARANCE
Visually check for malfunction of suspension component s, damage of air chamber of rear shock absorber,
installation malfunction, or defo rmation of vehicle height sensor.
Is the inspection result normal?
YES >> GO TO 2.
NO >> Repaire or replace damaged parts.
2.CHECK AIR LEAK
Apply soapy water to air tube, connecting portions between air tube and each component, and air chamber of
rear shock absorber. Check for air leakage.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repaire or replace damaged parts.
3.CHECK AIR COMPRESSOR RELAY POWER SUPPLY
1. Turn ignition switch OFF.
2. Check 30A fuse (#I).
3. Disconnect air compressor relay connector.
4. Check voltage between air compressor relay harness connector and ground.
DTC Display item Malfunction detected condition Possible cause
C1804 VHCL HEIGHT ADJ UP The vehicle height is 15 mm (0.59 in) or more lower
than the reference height despite the output of air
compressor ON signal continuously for 120 seconds
by the air levelizer control module.  Harness or connector
Air compressor
 Air compressor relay
 Air levelizer control module
 Rear shock absorber (air cham-
ber)
 Vehicle height sensor
 Air tube
 Rear suspension component parts
 Overloaded
Revision: 2010 May2011 QX56

SCS-84
< DTC/CIRCUIT DIAGNOSIS >[AIR LEVELIZER CONTROL SYSTEM]
C1808 AIR SUS COMPRS FNCTN
C1808 AIR SUS COMPRS FNCTN
DTC LogicINFOID:0000000006256080
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.PRECONDITIONING
If “DTC CONFIRMATION PROCEDURE” has been previous ly conducted, always turn ignition switch OFF
andwait at least 10 seconds before conducting the next test.
>> GO TO 2.
2.CHECK DTC DETECTION
With CONSULT-III
1. Set vehicle in the unloaded vehicle status.
2. Start the engine and wait 5 minutes or more.
3. Perform “Self Diagnostic Result” in “E-SUS”.
Is
“C1808” detected ?
YES >> Go to SCS-84, "DiagnosisProcedure".
NO >> INSPECTION END
Diagnosis ProcedureINFOID:0000000006256081
1.CHECK APPEARANCE
Visually check for malfunction of suspension component s, damage of air chamber of rear shock absorber,
installation malfunction, or deformation of vehicle height sensor.
Is the inspection result normal?
YES >> GO TO 2.
NO >> Repaire or replace damaged parts.
2.CHECK AIR LEAK
Apply soapy water to air tube, connecting portions between air tube and each component, and air chamber of
rear shock absorber. Check for air leakage.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repaire or replace damaged parts.
3.CHECK AIR COMPRESSOR RELAY POWER SUPPLY
1. Turn ignition switch OFF.
2. Check 30A fuse (#I).
3. Disconnect air compressor relay connector.
4. Check voltage between air compressor relay harness connector and ground.
DTC Display item Malfunction detected condition Possible cause
C1808 AIR SUS COMPRS FNCTN The cumulative operating time of the air compressor
reaches 180 seconds or more.
NOTE:
Cumulative time is cleared under the following condi-
tions:
 Ignition switch: OFF
 Exhaust conditions: satisfied [Vehicle height re-
mains 15 mm (0.59 in) or more higher than the ref-
erence height for 30 seconds.]  Harness or connector
 Vehicle height sensor
 Air compressor (exhaust sole-
noid)
 Air compressor relay
 Overloaded
 Rear shock absorber (air cham- ber)
 Rear suspension component parts
 Air tube
Revision: 2010 May2011 QX56