ground INFINITI QX56 2011 Factory Service Manual

POWER STEERING CONTROL UNITSTC-9
< ECU DIAGNOSIS INFORMATION >
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When using circuit tester or osci lloscope to measure voltage for in spection, be sure not to forcibly
extend any connector terminals.
Fail-Safe INFOID:0000000006256122
EPS system
 EPS system enters the fail-safe mode (that allows the steering
force to be controlled without impair ing the drivability) if any of the
input/output values to/from EPS system (power steering control
unit) deviate from the standard range.
 The power steering control unit controls the driving voltage to the
power steering solenoid valve for maintaining the power steering
assist force when the fail-safe function is activated. (The engine
speed signals control EPS system if any vehicle speed signal error
is detected.)
10
(B/SB) Ground Engine speed signal Input Engine is running
 Warm-up condition
 Idle speed
Engine is running
 Warm-up condition
 Engine speed: Approx. 2,000
rpm
Te r m i n a l N o .
(Wire color) Description
Condition Value (Approx.)
+ - Signal name Input/
OutputJPBIA3352ZZ
JPBIA3354ZZ
JPGIB0022GB
Error area and root cause Cancel condition
Engine speed is 1,500 rpm or more and there is no vehicle speed signal input for
over 10 seconds during vehicle travel.  When a vehicle speed signal of 2 km/h (1.2
MPH) or more is inputted.
 Ignition switch is turned OFF to ON.
Vehicle speed signal has abruptly dropped from 30 km/h (19 MPH) or more to 2
km/h (1.2 MPH) or less within 1.4 seconds.
Revision: 2010 May2011 QX56

STC-14
< DTC/CIRCUIT DIAGNOSIS >
POWER SUPPLY AND GROUND CIRCUIT
DTC/CIRCUIT DIAGNOSIS
POWER SUPPLY AND GROUND CIRCUIT
Diagnosis ProcedureINFOID:0000000006256125
1.CHECK POWER SUPPLY (1)
1. Turn the ignition switch OFF.
2. Disconnect power steering control unit harness connector.
3. Check the voltage between power steering control unit harness connector and ground.
4. Turn the ignition switch ON. CAUTION:
Never start the engine.
5. Check the voltage between power steering control unit harness connector and ground.
Is the inspection result normal?
YES >> GO TO 3.
NO >> GO TO 2.
2.CHECK POWER SUPPLY (2)
1. Turn the ignition switch OFF.
2. Check 10A fuse (#3).
3. Disconnect fuse block (J/B) harness connector.
4. Check the continuity between power steering cont rol unit harness connector and fuse block (J/B) harness
connector.
5. Check the continuity between power st eering control unit harness connector and ground.
Is the inspection result normal?
YES >> Perform trouble diagnosis for ignition power supply circuit. Refer to PG-89, "Wiring Diagram -
IGNITION POWER SUPPLY -".
NO >> Repair or replace damaged parts.
3.CHECK GROUND CIRCUIT
1. Turn the ignition switch OFF.
2. Check the continuity between power st eering control unit harness connector and ground.
Power steering control unit
—Voltage
Connector Terminal
M108 3 Ground 0 V
Power steering control unit — Voltage
Connector Terminal
M108 3 Ground Battery voltage
Power steering control unit Fuse block (J/B) Continuity
Connector Terminal Connector Terminal
M108 3 M1 2A Existed
Power steering control unit —Continuity
Connector Terminal
M108 3 Ground Not existed
Revision: 2010 May2011 QX56

POWER SUPPLY AND GROUND CIRCUITSTC-15
< DTC/CIRCUIT DIAGNOSIS >
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Is the inspection result normal?
YES >> GO TO 4.
NO >> Repair or replace error-detected parts.
4.CHECK TERMINALS AND HARNESS CONNECTORS
Check the power steering control unit pin terminal s for damage or loose connection with harness connector.
Is the inspection result normal?
YES >> INSPECTION END
NO >> Repair or replace error-detected parts.
Power steering control unit
—Continuity
Connector Terminal
M108 6 Ground Existed
Revision: 2010 May2011 QX56

STC-16
< DTC/CIRCUIT DIAGNOSIS >
POWER STEERING SOLENOID VALVE
POWER STEERING SOLENOID VALVE
Component Function CheckINFOID:0000000006256126
1.CHECK POWER STEERING SOLENOID VALVE OPERATION
Check changes in steering force from a halt condition to high-speed driving.
Is the inspection result normal?
YES >> INSPECTION END
NO >> Check the power steering solenoid valve. Refer to STC-16, "
Diagnosis Procedure".
Diagnosis Procedure INFOID:0000000006256127
1.CHECK POWER STEERING SOLENOID VALVE SIGNAL
1. Turn the ignition switch OFF.
2. Check the voltage between power steering control unit harness connector and ground.
Is the inspection result normal?
YES >> GO TO 4.
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN POWER STEERING SO LENOID VALVE AND POWER STEERING CON-
TROL UNIT
1. Turn the ignition switch OFF.
2. Disconnect power steering solenoid valve harness connector.
3. Disconnect power steering control unit harness connector.
4. Check the continuity between power steering solenoid valve harness connector and the power steering
control unit harness connector.
5. Check the continuity between power st eering control unit harness connector and ground.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repair or replace error-detected parts.
3.CHECK POWER STEERING SOLENOID VALVE
Check the power steering solenoid valve. Refer to STC-17, "
Component Inspection".
Is the inspection result normal?
YES >> GO TO 4.
NO >> Replace gear-sub assembly. Refer to ST-43, "
Disassembly and Assembly".
Power steering control unit
— Condition Voltage (Approx.)
Connector Terminal
M108 1 Ground Vehicle speed: 0 km/h (0 MPH)
(Engine is running)
4.4 – 6.6 V
Vehicle speed: 100 km/h (62 MPH) 2.4 – 3.6 V
Power steering solenoid valve Power steering control unit Continuity
Connector Terminal Connector Terminal
F45 1
M108 1 Existed
25Existed
Power steering control unit — Continuity
Connector Terminal
M108 1
Ground Not existed
5
Revision: 2010 May2011 QX56

STC-18
< DTC/CIRCUIT DIAGNOSIS >
ENGINE SPEED SIGNAL CIRCUIT
ENGINE SPEED SIGNAL CIRCUIT
Diagnosis ProcedureINFOID:0000000006256129
1.PERFORM ECM SELF-DIAGNOSIS
With CONSULT-III
Perform “ENGINE” self-diagnosis.
Is any DTC detected?
YES >> Check the DTC. Refer to EC-98, "DTC Index".
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN ECM AND POWER STEERING CONTROL UNIT
1. Turn the ignition switch OFF.
2. Disconnect ECM harness connectors.
3. Disconnect power steering control unit harness connector.
4. Check the continuity between ECM harness connecto r and power steering control unit harness connector.
5. Check the continuity between power st eering control unit harness connector and ground.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repair or replace error-detected parts.
3.CHECK ENGINE SPEED SIGNAL (ECM)
1. Connect ECM harness connectors.
2. Check the signal between ECM harness connector and ground with oscilloscope.
Is the inspection result normal?
YES >> GO TO 4.
NO >> Replace ECM. Refer to EC-143, "
Description".
ECM Power steering control unit
Continuity
Connector Terminal Connector Terminal
E80 169 M108 10 Existed
Power steering control unit — Continuity
Connector Terminal
M108 10 Ground Not existed
ECM — Condition Voltage (Approx.)
Connector Terminal
E80 169 Ground Engine is running
 Warm-up condition
 Idle speed
Engine is running
 Warm-up condition
 Engine speed: Approx. 2,000 rpm
JPBIA3352ZZ
JPBIA3354ZZ
Revision: 2010 May2011 QX56

ENGINE SPEED SIGNAL CIRCUITSTC-19
< DTC/CIRCUIT DIAGNOSIS >
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4.CHECK ENGINE SPEED SIGNAL (P OWER STEERING CONTROL UNIT)
1. Turn the ignition switch OFF.
2. Connect power steering control unit harness connector.
3. Check the signal between power steering control unit harness connector and ground with oscilloscope.
Is the inspection result normal?
YES >> GO TO 5.
NO >> Replace power steering control unit. Refer to STC-23, "
Removal and Installation".
5.CHECK TERMINALS AND HARNESS CONNECTORS
 Check the power steering control unit pin terminal s for damage or loose connection with harness connector.
 Check the ECM pin terminals for damage or loose connection with harness connector.
Is the inspection result normal?
YES >> INSPECTION END
NO >> Repair or replace error-detected parts.
Power steering control unit — Condition Voltage (Approx.)
Connector Terminal
M108 10 Ground Engine is running
 Warm-up condition
 Idle speed
Engine is running
 Warm-up condition
 Engine speed: Approx. 2,000 rpm
JPBIA3352ZZ
JPBIA3354ZZ
Revision: 2010 May2011 QX56

STC-20
< DTC/CIRCUIT DIAGNOSIS >
VEHICLE SPEED SIGNAL CIRCUIT
VEHICLE SPEED SIGNAL CIRCUIT
Diagnosis ProcedureINFOID:0000000006256130
1.PERFORM COMBINATION METER SELF-DIAGNOSIS
With CONSULT-III
Perform “METER/M&A” self-diagnosis. Refer to MWI-30, "
CONSULT-III Function".
Is any DTC detected?
YES >> Check the DTC.
NO >> GO TO 2.
2.CHECK HARNESS BETWEEN COMBINATION ME TER AND POWER STEERING CONTROL UNIT
1. Turn the ignition switch OFF.
2. Disconnect combination meter harness connector.
3. Disconnect power steering control unit harness connector.
4. Check the continuity between combination meter harness connector and power steering control unit har-
ness connector.
5. Check the continuity between power st eering control unit harness connector and ground.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repair or replace error-detected parts.
3.CHECK VEHICLE SPEED SIGN AL (COMBINATION METER)
1. Connect combination meter harness connector.
2. Check the combination meter input/output standard values. Refer to MWI-35, "
Reference Value".
Is the inspection result normal?
YES >> GO TO 4.
NO >> Replace combination meter Refer to MWI-85, "
Removal and Installation".
4.CHECK VEHICLE SPEED SIGNAL (POWER STEERING CONTROL UNIT)
1. Turn the ignition switch OFF.
2. Connect power steering control unit harness connector.
3. Check the signal between power steering cont rol unit harness connector and ground with oscilloscope.
Combination meter Power steering control unit
Continuity
Connector Terminal Connector Terminal
M34 30 M108 8 Existed
Power steering control unit —Continuity
Connector Terminal
M108 8 Ground Not existed
Power steering control unit — Condition Voltage (Approx.)
Connector Terminal
M108 8 Ground Vehicle speed: 40 km/h (25 MPH)
CAUTION:
Check air pressure of tire under
standard condition.NOTE:
The maximum voltage varies de-
pending on the specification (desti-
nation unit).
JSNIA0015GB
Revision: 2010 May2011 QX56

STC-22
< SYMPTOM DIAGNOSIS >
UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIATION)
SYMPTOM DIAGNOSIS
UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIA-
TION)
Description INFOID:0000000006256131
 Hard steering when fully turning the steering wheel.
 Light steering when driving at a high speed.
Diagnosis Procedure INFOID:0000000006256132
1.CHECK SYSTEM FOR POWER SUPPLY AND GROUND
Perform trouble diagnosis for power supply and ground. Refer to STC-14, "
Diagnosis Procedure".
Is the inspection result normal?
YES >> GO TO 2.
NO >> Repair or replace error-detected parts.
2.CHECK SYSTEM FOR VEHICLE SPEED SIGNAL
Perform trouble diagnosis for vehicle speed signal. Refer to STC-20, "
Diagnosis Procedure".
Is the inspection result normal?
YES >> GO TO 3.
NO >> Repair or replace error-detected parts.
3.CHECK SYSTEM FOR ENGINE SPEED SIGNAL
Perform trouble diagnosis for engine speed signal. Refer to STC-18, "
Diagnosis Procedure".
Is the inspection result normal?
YES >> GO TO 4.
NO >> Repair or replace error-detected parts.
4.CHECK SYSTEM FOR POWER STEERING SOLENOID VALVE
Perform trouble diagnosis for power steering solenoid valve. Refer to STC-16, "
Diagnosis Procedure".
Is the inspection result normal?
YES >> Perform the symptom diagnosis for the steering system. Refer to ST-29, "NVH Troubleshooting
Chart".
NO >> Repair or replace error-detected parts.
Revision: 2010 May2011 QX56

STR-14
< DTC/CIRCUIT DIAGNOSIS >
B TERMINAL CIRCUIT
DTC/CIRCUIT DIAGNOSIS
B TERMINAL CIRCUIT
Diagnosis ProcedureINFOID:0000000006275524
CAUTION:
Perform diagnosis under the condition that engine cannot start by the following procedure.
1. Remove fuel pump fuse.
2. Crank or start the engine (where possi ble) until the fuel pressure is released.
1.CHECK “B” TERMINAL CIRCUIT
1. Turn ignition switch OFF.
2. Check that starter motor “B” terminal connection is clean and tight.
3. Check voltage between starter motor “B” terminal and ground.
Is the inspection result normal?
YES >> GO TO 2.
NO >> Check harness between battery and starter motor for open circuit.
2.CHECK BATTERY CABLE CONNECTION STATUS (VOLTAGE DROP TEST)
1. Shift A/T selector lever to “P” or “N” position.
2. Check voltage between battery positive terminal and starter motor “B” terminal.
Is the inspection result normal?
YES >> GO TO 3.
NO >> Check harness between the battery and the starter motor for poor continuity.
3.CHECK GROUND CIRCUIT STATUS (VOLTAGE DROP TEST)
1. Shift A/T selector lever to “P” or “N” position.
2. Check voltage between starter motor case and battery negative terminal.
Is the inspection result normal?
YES >> “B” terminal circuit is OK. Further inspection is necessary. Refer to STR-11, "Work Flow".
NO >> Check the starter motor case and ground for poor continuity.
(+) (–) Voltage
Starter motor “B” terminal
F57 2 Ground Battery voltage
(+) (–)
ConditionVoltage (V)
(Approx.)
Starter motor “B” terminal
Battery positive terminal F57 2 When the ignition switch
is in START position Less than 0.5
(+) (–) Condition Voltage (V)
(Approx.)
Starter motor case Battery negative terminal When the ignition switch is in START position Less than 0.2
Revision: 2010 May2011 QX56

S CONNECTOR CIRCUITSTR-15
< DTC/CIRCUIT DIAGNOSIS >
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S CONNECTOR CIRCUIT
Diagnosis ProcedureINFOID:0000000006275525
CAUTION:
Perform diagnosis under the cond
ition that engine cannot start by the following procedure.
1. Remove fuel pump fuse.
2. Crank or start the engine (where possi ble) until the fuel pressure is released.
1.CHECK “S” CONNECTOR CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect starter motor connector.
3. Shift A/T selector lever to “P” or “N” position.
4. Check voltage between starter motor harness connector and ground.
Is the inspection result normal?
YES >> “S” connector circuit is OK. Furt her inspection is necessary. Refer to STR-11, "Work Flow".
NO >> GO TO 2.
2.CHECK HARNESS CONTI NUITY (OPEN CIRCUIT)
1. Turn ignition switch OFF.
2. Disconnect IPDM E/R harness connector.
3. Check continuity between starter motor harness connector and IPDM E/R harness connector.
Is the inspection result normal?
YES >> Further inspection is necessary. Refer to SEC-48, "Work Flow".
NO >> Repair the harness or connector.
(+)
(–) Condition Voltage
Starter motor
Connector Terminal
F55 1 Ground When the ignition switch
is in START position Battery voltage
Starter motor harness IPDM E/R
Continuity
Connector Terminal Connector Terminal
F55 1 E10 3 Existed
Revision: 2010 May2011 QX56