2011 INFINITI QX56 ignition

C1801 VHCL HEIGHT SENSORSCS-69
< DTC/CIRCUIT DIAGNOSIS > [AIR LEVELIZER CONTROL SYSTEM]
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DTC/CIRCUIT DIAGNOSIS
C1801 VHCL HEIGHT SENSOR
DTC LogicINFOID:0000000006256062
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. Turn ignition switch ON and wait 60 seconds or more.
2. Perform “Self Diagnostic Results” in “E-SUS”.
Is
“C1801” detected ?
YES >> Go to SCS-69, "DiagnosisProcedure".
NO >> INSPECTION END
Diagnosis ProcedureINFOID:0000000006256063
1.CHECK APPEARANCE
Visually check for malfunction of suspension components, installing malfunction, or deformation of vehicle
height sensor.
Is the inspection result normal?
YES >> GO TO 2.
NO >> Repaire or replace damaged parts.
2.CHECK POWER SUPPLY CIRCUIT (PART 1)
1. Disconnect vehicle height sensor connector.
2. Turn ignition switch ON. CAUTION:
Never start the engine.
3. Check voltage between vehicle height sensor harness connector and ground.
Is the inspection result normal?
YES >> GO TO 4.
NO >> GO TO 3.
3.CHECK POWER SUPPLY CIRCUIT (PART 2)
1. Turn ignition switch OFF.
2. Disconnect air levelizer control module connector.
DTC Display itemI Malfunction detected condition Possible cause
C1801 VHCL HEIGHT SENSOR Signal voltage of the vehicle height sensor remains 0.2
V or less or 4.6 V or more continuously for 60 seconds
during sensor voltage (4.5 – 5.5 V) output by the air lev-
elizer control module.  Harness or connectors
(Sensor circuit is open.)
 Vehicle height sensor
 Air levelizer control module
 Rear suspension component parts
Vehicle height sensor —Voltage
Connector Terminal
C13 1 Ground 4.5 – 5.5 V
Revision: 2010 May2011 QX56

SCS-70
< DTC/CIRCUIT DIAGNOSIS >[AIR LEVELIZER CONTROL SYSTEM]
C1801 VHCL HEIGHT SENSOR
3. Check continuity between air levelizer control m
odule harness connector and vehicle height sensor har-
ness connector.
4. Check continuity between air levelizer control module harness connector and ground.
Is the inspection result normal?
YES >> 1. Check intermittent incident. Refer to GI-40, "Intermittent Incident".
2. If inspection result is OK, replace the air levelizer control module. Refer to SCS-94, "
Removal
and Installation".
NO >> Repair or replace damaged parts.
4.CHECK HARNESS BETWEEN AIR LEVELIZER CO NTROL MODULE AND VEHICLE HEIGHT SENSOR
1. Turn ignition switch OFF.
2. Disconnect air levelizer control module connector.
3. Check continuity between air levelizer control m odule harness connector and vehicle height sensor har-
ness connector.
4. Check continuity between air levelizer control module harness connector and ground.
Are the inspection results normal?
YES >> GO TO 5.
NO >> Repair or replace damaged parts.
5.CHECK VEHICLE HEIGHT SENSOR
Check the vehicle height sensor. Refer to SCS-70, "
Component Inspection".
Is the inspection result normal?
YES >> GO TO 6.
NO >> Replace the vehicle height sensor. Refer to SCS-98, "
Removal and Installation".
6.CHECK INTERMITTENT INCIDENT
Refer to GI-40, "
Intermittent Incident".
Is the inspection result normal?
YES >> Replace the air levelizer control module. Refer to SCS-94, "Removal and Installation".
NO >> Repair or replace damaged parts.
Component InspectionINFOID:0000000006256064
1.CHECK VEHICLE HEIGHT SENSOR
Air levelizer control module Vehicle height sensor Continuity
Connector Terminal Connector Terminal
B84 13 C13 1 Existed
Air levelizer control module —Continuity
Connector Terminal
B84 13 Ground Not existed
Air levelizer control module Vehicle height sensor Continuity
Connector Terminal Connector Terminal
B84 5
C13 2
Existed
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Air levelizer control module —Continuity
Connector Terminal
B84 5
Ground Not existed
4
Revision: 2010 May2011 QX56

SCS-72
< DTC/CIRCUIT DIAGNOSIS >[AIR LEVELIZER CONTROL SYSTEM]
C1802 AIR SUS COMPRS RELAY
C1802 AIR SUS COMPRS RELAY
DTC LogicINFOID:0000000006256065
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. Turn ignition switch ON and wait 10 seconds or more.
2. Select “COMPRESSOR” in “Active Test” in “E-SUS”.
3. Touch “ON” and wait 5 seconds or more.
4. Select “Self Diagnostic Result” in “E-SUS”.
Is
“C1802” detected ?
YES >> Go to SCS-72, "DiagnosisProcedure".
NO >> INSPECTION END
Diagnosis ProcedureINFOID:0000000006256066
1.CHECK AIR COMPRESSOR ON SIGNAL FROM AIR LEVELIZER CONTROL MODULE
CONSULT-III
1. Disconnect air compressor relay connector.
2. Turn ignition switch ON. CAUTION:
Never start the engine.
3. Select “COMPRESSOR” in “Active Test” in “E-SUS”.
4. Touch “ON”.
5. While operating test item, check voltage betw een air compressor relay harness connector and ground.
Is the inspection result normal?
YES >> GO TO 4.
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN AIR LEVELIZER CO NTROL MODULE AND AIR COMPRESSOR RELAY
1. Turn ignition switch OFF.
2. Disconnect air levelizer control module connector.
DTC Display item Malfunction detected condition Possible cause
C1802 AIR SUS COMPRS RELAY  Output voltage of the air compressor relay remains
9 V or less continuously for 5 seconds during air
compressor ON signal output by the air levelizer
control module.
 Output voltage of the air compressor relay remains
2 V or more continuously for 10 seconds during air
compressor OFF signal output by the air levelizer
control module.  Harness or connector
 Air compressor relay
 Air levelizer control module
Air compressor relay
—Voltage
Connector Terminal
E116 2 Ground 9 – 16 V
Revision: 2010 May2011 QX56

C1802 AIR SUS COMPRS RELAYSCS-73
< DTC/CIRCUIT DIAGNOSIS > [AIR LEVELIZER CONTROL SYSTEM]
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3. Check continuity between air levelizer control module harness connector and air compressor relay har-
ness connector.
4. Check continuity between air levelizer control module harness connector and ground.
5. Check voltage between air levelizer control module harness connector and ground.
Are the inspection results normal?
YES >> GO TO 3.
NO >> Repair or replace damaged part.
3.CHECK INTERMITTENT INCIDENT
Refer to GI-40, "
Intermittent Incident".
Is the inspection result normal?
YES >> Replace the air levelizer control module. Refer to SCS-94, "Removal and Installation".
NO >> Repair or replace damaged parts.
4.CHECK AIR COMPRESSOR RELAY GROUND
1. Turn ignition switch OFF.
2. Check continuity between air compressor relay harness connector and ground.
Is the inspection result normal?
YES >> GO TO 5.
NO >> Repair or replace damaged part.
5.CHECK AIR COMPRESSOR RELAY
1. Remove the air compressor relay. Refer to SCS-50, "
Component Parts Location".
2. Check continuity between air compressor relay harness connector terminals.
Is the inspection result normal?
YES >> Check intermittent incident. Refer to GI-40, "Intermittent Incident".
NO >> Replace the air compressor relay. Refer to SCS-50, "
Component Parts Location".
Air levelizer control module Air compressor relay
Continuity
Connector Terminal Connector Terminal
B84 3 E116 2 Existed
Air levelizer control module
—Continuity
Connector Terminal
B84 3 Ground Not existed
Air levelizer control module
—Voltage
Connector Terminal
B84 3 Ground 0 V
Air compressor relay —Continuity
Connector Terminal
E116 1 Ground Existed
Air compressor relay Continuity
Te r m i n a l
12Existed
Revision: 2010 May2011 QX56

SCS-74
< DTC/CIRCUIT DIAGNOSIS >[AIR LEVELIZER CONTROL SYSTEM]
C1803 AIR SUSPENSION EXH SOL
C1803 AIR SUSPENSION EXH SOL
DTC LogicINFOID:0000000006256067
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. Turn ignition switch ON and wait 10 seconds or more.
2. Select “EXHAUST SOLENOID” in “Active Test” in “E-SUS”.
3. Touch “ON” and wait 5 seconds or more.
4. Select “Self Diagnostic Result” in “E-SUS”.
Is
“C1803” detected ?
YES >> Go to SCS-74, "DiagnosisProcedure".
NO >> INSPECTION END
Diagnosis ProcedureINFOID:0000000006256068
1.CHECK EXHAUST SOLENOID ON SIGNAL FROM AIR LEVELIZER CONTROL MODULE
CONSULT-III
1. Disconnect air compressor harness connector.
2. Turn ignition switch ON. CAUTION:
Never start the engine.
3. Select “EXHAUST SOLENOID” in “Active Test” in “E-SUS”.
4. Touch “ON”.
5. While operating test item, check voltage bet ween air compressor harness connector and ground.
Is the inspection result normal?
YES >> GO TO 4.
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN AIR LEVELIZE R CONTROL MODULE AND AIR COMPRESSOR
1. Turn ignition switch OFF.
2. Disconnect air levelizer control module harness connector.
DTC Display item Malfunction detected condition Possible cause
C1803 AIR SUS EXH SOL  Output voltage of the exhaust solenoid remains 9 V
or less continuously for 5 seconds during exhaust
solenoid ON signal output by the air levelizer con-
trol module.
 Output voltage of the exhaust solenoid remains 2 V
or more continuously for 10 seconds during ex-
haust solenoid ON signal output by the air levelizer
control module.  Harness or connector
 Exhaust solenoid
 Air levelizer control module
Air compressor
—Voltage
Connector Terminal
C12 4 Ground 9 – 16 V
Revision: 2010 May2011 QX56

C1803 AIR SUSPENSION EXH SOLSCS-75
< DTC/CIRCUIT DIAGNOSIS > [AIR LEVELIZER CONTROL SYSTEM]
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3. Check continuity between air levelizer contro l module harness connector and air compressor harness
connector.
4. Check continuity between air levelizer control module harness connector and ground.
Are the inspection results normal?
YES >> GO TO 3.
NO >> Repair or replace damaged part.
3.CHECK INTERMITTENT INCIDENT
Refer to GI-40, "
Intermittent Incident".
Is the inspection result normal?
YES >> Replace the air levelizer control module. Refer to SCS-94, "Removal and Installation".
NO >> Repair or replace damaged parts.
4.CHECK AIR COMPRESSOR GROUND
1. Turn ignition switch OFF.
2. Check continuity between air compressor harness connector and ground.
Are the inspection results normal?
YES >> GO TO 5.
NO >> Repair or replace damaged part.
5.CHECK AIR COMPRESSOR (EXHAUST SOLENOID)
Check the air compressor (exhaust solenoid). Refer to SCS-75, "
Component Inspection".
Is the inspection result normal?
YES >> Check intermittent incident. Refer to GI-40, "Intermittent Incident".
NO >> Replace the air compressor. Refer to SCS-95, "
Removal and Installation".
Component InspectionINFOID:0000000006256069
CAUTION:
 Keep the inside of air compressor free of dust.
 Keep the resin stick and resin pipe free of scratches and burrs.
1.CHECK AIR COMPRESSOR (EXHAUST SOLENOID)
1. Remove the air compressor. Refer to SCS-95, "
Removal and Installation".
Air levelizer control module Air compressor
Continuity
Connector Terminal Connector Terminal
B84 11 C12 4 Existed
Air levelizer control module
—Continuity
Connector Terminal
B84 11 Ground Not existed
Air compressor —Continuity
Connector Terminal
C12 3 Ground Existed
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-78
< DTC/CIRCUIT DIAGNOSIS >[AIR LEVELIZER CONTROL SYSTEM]
C1804 VHCL HEIGHT ADJ UP
Is the inspection result normal?
YES >> GO TO 4.
NO >> Repair or replace damaged part.
4.CHECK AIR COMPRESSOR
RELAY OUTPUT CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect air compressor connector.
3. Check continuity between air compressor relay harness connector and air compressor harness connector.
4. Check continuity between air compressor relay harness connector and ground.
Are the inspection results normal?
YES >> GO TO 5.
NO >> Repair or replace damaged part.
5.CHECK AIR COMPRESSOR GROUND
Check continuity between air compressor harness connector and ground.
Are the inspection results normal?
YES >> GO TO 6.
NO >> Repair or replace damaged part.
6.CHECK AIR COMPRESSOR RELAY
Check the air compressor relay. Refer to SCS-79, "
Component Inspection (Air Compressor Relay)".
Is the inspection result normal?
YES >> GO TO 7.
NO >> Replace the air compressor relay.
7.CHECK AIR COMPRESSOR
Check the air compressor. Refer to SCS-79, "
Component Inspection (Air Compressor)".
Is the inspection result normal?
YES >> GO TO 8.
NO >> Replace the air compressor. Refer to SCS-95, "
Removal and Installation".
8.CHECK INTERMITTENT INCIDENT
Refer to GI-40, "
Intermittent Incident".
Is the inspection result normal?
YES >> 1. Perform “STANDARD VEHICLE HEIGHT SETTING”. Refer to SCS-67, "Work Procedure".
2. If DTC is detected, replace the air levelizer control module. Refer to SCS-94, "
Removal and
Installation".
Air compressor relay
—Voltage
Connector Terminal
E116 5 Ground Battery voltage
Air compressor rela y Air compressor
Continuity
Connector Terminal Connector Terminal
E116 3 C12 1 Existed
Air compressor relay —Continuity
Connector Terminal
E116 3 Ground Not existed
Air compressor —Continuity
Connector Terminal
C12 2 Ground Existed
Revision: 2010 May2011 QX56