2007 INFINITI QX56 suspension

RSU-6
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
TROUBLE DIAGNOSIS
How to Perform Trouble Diagnosis for Quick and Accurate RepairINFOID:0000000003532657
INTRODUCTION
The rear load leveling air suspension system uses an electronic con-
trol unit to control major functions. The control unit accepts input sig-
nals from the height sensor and controls compressor and exhaust
valve operation.
It is much more difficult to diagnose a rear load leveling air suspen-
sion system problem that occurs intermittently rather than continu-
ously. Most intermittent problems are caused by poor electrical
connections or faulty wiring. In this case, careful checking of suspi-
cious circuits may help prevent the replacement of good parts.
Before undertaking actual checks, take just a few minutes to talk with
a customer who approaches with an air suspension system com-
plaint. The customer is a very good source of information on such
problems, especially intermittent ones. Through discussion with the
customer, find out what symptoms are present and under what con-
ditions they occur.
Start your diagnosis by looking for basic mechanical problems first.
This is one of the best ways to troubleshoot concerns on an air sus-
pension system equipped vehicle. Also check related Service Bulle-
tins for information.
CLARIFY CONCERN
• A customer's description of a vehicle concern may vary depending
on the individual. It is important to clarify the customer's concern.
• Ask the customer about what symptoms are present under what
conditions. Use this information to reproduce the symptom.
SEF233G
SEF234G
SBR339B

RSU-10
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
Basic Inspection
INFOID:0000000003532660
AIR HOSES
1. Check for pinched or damaged air hoses between the suspension air reservoir and each load leveling rear
air suspension shock absorber. Reposition, repair or replace hoses as necessary.
2. Check the air hose connections at the suspension air reservoir and at the shock absorbers for leaks. If
connections are leaking, repair or replace hoses as necessary.
WEWA0070E

TROUBLE DIAGNOSIS
RSU-11
< SERVICE INFORMATION >
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POWER SYSTEM TERMINAL LOOSENESS AND BATTERY INSPECTION
Make sure the battery positive cable, negative cable and ground connection are not loose. In addition, make
sure the battery is sufficiently charged.
CK SUSP INDICATOR LAMP INSPECTION
1. Make sure the CK SUSP indicator lamp turns on for approximately 2 seconds when the ignition switch is
turned ON. If it does not, check the combination meter. Refer to DI-5
.
2. Make sure the lamp turns off approximately 2 seconds after the ignition switch is turned ON. If the lamp
does not turn off, conduct self-diagnosis of the suspension control unit.
3. After conducting the self-diagnosis, be sure to erase the error memory. Refer to RSU-11, "
CONSULT-II
Function (AIR LEVELIZER)" .
Chek Suspension Indicator Lamp TimingINFOID:0000000003532661
X: ON
—: OFF
Control Unit Input/Output Signal StandardINFOID:0000000003532662
CONSULT-II Function (AIR LEVELIZER)INFOID:0000000003532663
CONSULT-II can display each diagnostic item using the diagnostic test modes shown following.
CONSULT-II START PROCEDURE
Refer to GI-36, "CONSULT-II Start Procedure".
ConditionCK SUSP
indicator lampRemarks
Ignition switch OFF – –
Ignition switch ON X Turns off after approximately 2 seconds.
Te r m i n a l
No.Wire color Item ConditionVoltage (V)
(Approx.)
1 V Compressor relay output
Ignition switch ON or STARTBattery voltage
3 W Height sensor signal input 0.2V - 4.8V
5 R Reference voltage 5V
6 G/R Ignition power
Battery voltage
7W/LBattery power —
8 G/W Diagnostic K-line — —
9 SB Exhaust valve output Ignition switch ON or START Battery voltage
10 BR Warning lamp output — —
14 L Height sensor ground — —
15 BR/W Generator L signal input Engine running —
16 B Suspension control unit ground — 0V
AIR LEVELIZER
diagnostic modeDescription
WORK SUPPORTSupports inspections and adjustments. Commands are transmitted to the BCM for setting the status
suitable for required operation, input/output signals are received from the BCM 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 Suspension control unit part number can be read.

RSU-12
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS
SELF-DIAGNOSIS
Display Item List
WORK SUPPORT
Display Item List
DATA MONITOR
Display Item List
Self-diagnostic item Malfunction detecting condition Check system
Vehicle height sensor
[C1801]Vehicle height sensor voltage is less than 0.2V or greater than
4.8V for more than 60 seconds.Refer to RSU-14, "
Height
Sensor System Inspection" .
Compressor relay
[C1802]1. Driving transistor for compressor relay is off and monitor
voltage continues high level for more than 10 seconds.
2. Driving transistor for compressor relay is on and monitor
voltage continues low level for more than 5 seconds.Refer to RSU-17, "
Compres-
sor Motor, Compressor Motor
Relay and Circuit Inspection"
.
Exhaust solenoid
[C1803]1. Driving transistor for exhaust solenoid is off and monitor volt-
age continues high level for more than 10 seconds.
2. Driving transistor for exhaust solenoid is on and monitor volt-
age continues low level for more than 5 seconds.Refer to RSU-15, "
Exhaust
Valve Solenoid System In-
spection" .
Vehicle height adjusting trouble
(compressor)
[C1804]Continuous compressor relay ON time is more than 120 seconds.Refer to RSU-17, "
Compres-
sor Motor, Compressor Motor
Relay and Circuit Inspection"
.
Vehicle height adjusting trouble
(exhaust solenoid)
[C1805]Continuous exhaust solenoid ON time is more than 120 seconds.Refer to RSU-15, "
Exhaust
Valve Solenoid System In-
spection" .
Vehicle height sensor locking trou-
ble
[C1806]Output sensor voltage variation ±0.02V is more than 100 hour
when vehicle height range is normal.Refer to RSU-14, "
Height
Sensor System Inspection".
Sensor 5V trouble
[C1807]Sensor reference voltage is less than 0.8V or more than 6V for 20
seconds.Refer to RSU-14, "
Height
Sensor System Inspection".
Integral time trouble by supplying
air
[C1808]Integral discontinuous time on the compressor is more than 180
seconds.Refer to RSU-17, "
Compres-
sor Motor, Compressor Motor
Relay and Circuit Inspec-
tion".
Item Description Condition
STANDARD HEIGHT LEVELResets the vehicle height to the initialization flag set-
ting stored in the suspension control unit.Vehicle unladen RSU-44, "
Wheelarch Height
(Unladen*1)" , set in a horizontal position and
not moving.
NOTE:
Do not take your eyes off the vehicle while
CONSULT-II is processing.
ADJUST HEIGHT INISets the height initialization flag in the suspension
control unit when the control unit has been replaced
or when the initialization flag has been cleared using
the "CLEAR HEIGHT INI" procedure.Vehicle unladen RSU-44, "
Wheelarch Height
(Unladen*1)" . Move vehicle forward and back-
ward approx. 5 m (16.4 ft) and rock vehicle from
side to side.
NOTE:
Do not move vehicle while CONSULT-II is pro-
cessing.
CLEAR HEIGHT INIClears the initialization flag in the suspension control
unit.Vehicle unladen RSU-44, "
Wheelarch Height
(Unladen*1)" .

TROUBLE DIAGNOSIS
RSU-13
< SERVICE INFORMATION >
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X: Applicable
–: Not applicable
ACTIVE TEST
CAUTION:
• Do not perform active test while driving.
Display Item List
CAUTION:
The "COMPRESSOR" active test will remain ON until it is turned off using CONSULT-II. Allowing the
compressor to run for an extended period of time may cause damage to air suspension system com-
ponents due to excessive pressure in the air suspension system.
NOTE:
• "TEST IS STOPPED" is displayed approximately 10 seconds after operation starts for all active test items
except "COMPRESSOR".
• After "TEST IS STOPPED" is displayed, to perform test again, repeat Step 6.
Test ItemData monitor item selection
ALL
SIGNALSSELECTION
FROM MENU
HEIGT SENXX
HEIGT CALCXX
SEN FIX TIME X X
HEIGT INI VAL X X
COMPRESSOR X X
EXH SOLENOID X X
ACG LXX
Test Item Description
COMPRESSOROFF/ON
EXHAUST SOLENOID OFF/ON
WARNING LAMPOFF/ON

RSU-14
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS FOR SELF-DIAGNOSTIC ITEMS
TROUBLE DIAGNOSIS FOR SELF-DIAGNOSTIC ITEMS
Height Sensor System InspectionINFOID:0000000003532664
INSPECTION PROCEDURE
1.SELF-DIAGNOSIS RESULT CHECK
Check self-diagnosis results.
Is the above displayed in the self-diagnosis display items?
YES >> GO TO 3.
NO >> GO TO 2.
2.DATA MONITOR CHECK
Conduct data monitor of "HEIGT SEN" to check if the status is normal.
OK or NG
OK >> Inspection End.
NG >> GO TO 3.
3.CONNECTOR INSPECTION
1. Disconnect suspension control unit connector B3 and height sensor C8.
2. Check the terminals for deformation, disconnection, looseness or damage.
OK or NG
OK >> GO TO 4.
NG >> Repair or replace as necessary.
4.CHECK HEIGHT SENSOR POWER
1. Reconnect the suspension control unit connector.
2. Turn the ignition switch ON.
3. Check voltage between height sensor connector C8 terminal 1
and ground.
OK or NG
OK >> GO TO 5.
NG >> Check harness or connector for open or short. If OK,
replace suspension control unit. Refer to RSU-42
.
5.CHECK HEIGHT SENSOR GROUND
1. Turn ignition switch OFF.
Self-diagnosis results
C1801
C1806
C1807
HEIGT SEN 0.2V - 4.8V
Voltage : Approx. 5V
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TROUBLE DIAGNOSIS FOR SELF-DIAGNOSTIC ITEMS
RSU-15
< SERVICE INFORMATION >
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2. Check continuity between height sensor connector C8 terminal
3 and ground.
OK or NG
OK >> GO TO 6.
NG >> Repair harness or connector.
6.CHECK HEIGHT SENSOR SIGNAL CIRCUIT
1. Disconnect suspension control unit connector.
2. Check continuity between height sensor connector C8 terminal
2 and suspension control unit connector B3 terminal 3.
3. Check continuity between height sensor connector C8 terminal
2 and ground.
OK or NG
OK >> Replace the height sensor. Refer to RSU-40.
NG >> Repair harness or connector.
Exhaust Valve Solenoid System InspectionINFOID:0000000003532665
INSPECTION PROCEDURE
1.SELF-DIAGNOSIS RESULT CHECK
Check self-diagnosis results.
Is the above displayed in the self-diagnosis display items?
YES >> If code C1803 was retrieved during self-diagnosis, GO TO 3. If code C1805 was retrieved during
self-diagnosis, GO TO 2.
NO >> Inspection End.
2.CHECK SYSTEM OPERATION
1. Load vehicle to standard laden condition (with driver, front passenger, 2 passengers in second row seats
and no cargo).
2. Conduct active test of "COMPRESSOR" to raise vehicle ride height to +20mm.
CAUTION:3 - Ground Continuity should exist.
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2 - 3 Continuity should exist.
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2 - Ground Continuity should not exist.
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Self-diagnosis results
C1803
C1805

RSU-16
< SERVICE INFORMATION >
TROUBLE DIAGNOSIS FOR SELF-DIAGNOSTIC ITEMS
The "COMPRESSOR" active test will remain ON until it is turned off using CONSULT-II. Allowing
the compressor to run for an extended period of time may cause damage to air suspension sys-
tem components due to excessive pressure in the air suspension system.
3. Return the rear load leveling air suspension system to normal operating mode.
4. Check self-diagnostic results.
Is code C1805 displayed again?
YES >> GO TO 3.
NO >> Inspection End.
3.CONNECTOR INSPECTION
1. Disconnect suspension control unit connector B3 and suspension air compressor C9.
2. Check the terminals for deformation, disconnection, looseness or damage.
OK or NG
OK >> If code C1805 was retrieved during self-diagnosis, GO TO 4. If code C1803 was retrieved during
self-diagnosis, GO TO 6.
NG >> Repair or replace as necessary.
4.AIR HOSE INSPECTION
Inspect for pinched or damaged air hoses between the suspension air reservoir and each load leveling rear air
suspension shock absorber.
OK or NG
OK >> GO TO 5.
NG >> Repair or replace as necessary.
5.EXHAUST VALVE SOLENOID INSPECTION
Apply 12V to suspension air compressor terminal 2 and ground to
suspension air compressor terminal 1.
OK or NG
OK >> GO TO 6.
NG >> Replace the suspension air compressor. Refer to RSU-
38.
6.CHECK EXHAUST VALVE SOLENOID POWER AND GROUND
1. Reconnect the suspension control unit connector.
2. Turn the ignition switch ON.
3. Check voltage between suspension air compressor connector
C9 terminal 2 and ground.
4. Turn ignition switch OFF.System air pressure should vent.
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Voltage : Approx. 12V
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