2008 INFINITI QX56 suspension

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
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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

SCS-8
< FUNCTION DIAGNOSIS >
DIAGNOSIS SYSTEM (SUSPENSION CONTROL UNIT)
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 suspension control sys-
tem components due to excessive pressure.
NOTE:
• "TEST IS STOPPED" is displayed approximately 10 seconds after operation starts for all active test items except "COMPRESSOR".
• After "TEST IS STOPPED" is display ed, to perform test again, repeat step 6.
Test Item Description
COMPRESSOR ON/OFF
EXHAUST SOLENOID ON/OFF
WARNING LAMP ON/OFF
Revision: March 2010 2008 QX56

C1801 VEHICLE HEIGHT SENSORSCS-9
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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

C1803 EXHAUST SOLENOIDSCS-11
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C1803 EXHAUST SOLENOID
DescriptionINFOID:0000000001731966
The exhaust valve solenoid controls the vent function of the suspensi on control system. The exhaust valve
solenoid is built into the suspension air compressor. The suspension control unit supplies voltage to the
exhaust valve solenoid to activate it.
DTC LogicINFOID:0000000001731967
DTC DETECTION LOGIC
Diagnosis ProcedureINFOID:0000000001731968
1.CHECK EXHAUST SOLENOID OPERATION
CAUTION:
While operating this active test, the suspension control system wil l vent air pressure and the vehicle
ride height will lower. Ensure th e area around the vehicle is free from obstructions before beginning
test.
CONSULT-III
1. Ensure the suspension control system has air pressure and is not drooping in the rear.
2. Select "EXHAUST SOLENOID" of AIR LEVELIZER active test items.
3. While operating test item, check that the exhaust va lve solenoid opens to vent air from the system. The
vehicle should lower when the exhaust valve solenoid is activated.
Does the system vent properly?
YES >> Exhaust valve solenoid is operating normally.
NO >> Refer to SCS-23, "
Description"
DTCDisplay contents of CON-
SULT-III Diagnostic item is detected when ...
Probable malfunction location
C1803 EXHAUST SOLENOID • Driving transistor for the exhaust valve sole-
noid is OFF and monitor voltage continues at
a high level for more than 10 seconds.
• Driving transistor for the exhaust valve sole-
noid is ON and monitor voltage continues at
a low level for more than 5 seconds. Open or short circuit in the exhaust valve sole-
noid control circuit. Refer to
SCS-23, "
Compo-
nent Function Check"
ON : Air vents and vehicle ride height lowers
OFF : No air vents and vehicle ride height remains constant
Revision: March 2010 2008 QX56