2001 INFINITI QX4 power steering

TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
42 B/Y Start signal[Ignition switch ªONº]Approximately 0V
[Ignition switch ªSTARTº]9 - 12V
43 R Ignition switch[Ignition switch ªOFFº]0V
[Ignition switch ªONº]BATTERY VOLTAGE
(11 - 14V)
44 L PNP switch[Ignition switch ªONº]
IGear position is ªPº or ªNº.Approximately 0V
[Ignition switch ªONº]
IExcept the above gear positionBATTERY VOLTAGE
(11 - 14V)
45 B/RAir conditioner switch
signal[Engine is running]
IBoth A/C switch and blower switch are ªONº.Approximately 0V
[Engine is running]
IA/C switch is ªOFFº.Approximately 5V
47 R/BPower steering oil
pressure switch[Engine is running]
ISteering wheel is being turned.0 - 1.0V
[Engine is running]
ISteering wheel is not being turned.Approximately 5V
48 B ECM ground[Engine is running]
IIdle speedEngine ground
51 BR A/C cut signal[Engine is running]
IAir conditioner is operating.0 - 0.5V
52 PU Electrical load signal[Engine is running]
IRear window defogger: ON
IHi-beam headlamp: ONBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
IElectrical load: OFF0V
55 W/BSwirl control valve con-
trol vacuum check
switch[Engine is running]
IIdle speed
IEngine coolant temperature is between 15 to
50ÉC (59 to 122ÉF).Approximately 5V
[Engine is running]
IIdle speed
IEngine coolant temperature is above 55ÉC
(131ÉF).0 - 1.0V
56 OR/LThrottle position switch
(Closed position)[Engine is running]
IAccelerator pedal fully releasedBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
IAccelerator pedal depressedApproximately 0V
57 B ECM ground[Engine is running]
IIdle speedEngine ground
58 B/P Sensors' ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
59 BFuel level sensor
ground[Engine is running]
IIdle speedApproximately 0V
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
ECM Terminals and Reference Value (Cont'd)
EC-131

DescriptionNBEC0249SYSTEM DESCRIPTIONNBEC0249S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed (POS signal)
Idle air
controlIACV-AAC valve Crankshaft position sensor (REF) Engine speed (REF signal)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Throttle position sensor Throttle position
Park/neutral position (PNP) switch Park/neutral position
Air conditioner switch Air conditioner operation
Power steering oil pressure switch Power steering load signal
Battery Battery voltage
Vehicle speed sensor Vehicle speed
Ambient air temperature switch Ambient air temperature
Intake air temperature sensor Intake air temperature
Absolute pressure sensor Ambient barometic pressure
This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which by-passes the throttle valve via IACV-AAC
valve. The IACV-AAC valve changes the opening of the air by-pass
passage to control the amount of auxiliary air. This valve is actu-
ated by a step motor built into the valve, which moves the valve in
the axial direction in steps corresponding to the ECM output sig-
nals. One step of IACV-AAC valve movement causes the respec-
tive opening of the air by-pass passage. (i.e. when the step
advances, the opening is enlarged.) The opening of the valve is
varied to allow for optimum control of the engine idling speed. The
crankshaft position sensor (POS) detects the actual engine speed
and sends a signal to the ECM. The ECM then controls the step
position of the IACV-AAC valve so that engine speed coincides with
the target value memorized in ECM. The target engine speed is the
lowest speed at which the engine can operate steadily. The opti-
mum value stored in the ECM is determined by takig into consid-
eration various engine conditions, such as during warm up,
deceleration, and engine load (air conditioner, power steering and
cooling fan operation).
SEF765P
COMPONENT DESCRIPTIONNBEC0249S02IACV-AAC ValveNBEC0249S0201The IACV-AAC valve is operated by a step motor for centralized
control of auxiliary air supply. This motor has four winding phases
and is actuated by the output signals of ECM which turns ON and
OFF two windings each in seqeunce. Each time the IACV-AAC
valve opens or closes to change tha auxiliary air quantity, the ECM
sends a pulse signal to the step motor. When no change in the
auxiliary air quantity is needed, the ECM does not issue the pulse
signal. A certain voltage signal is issued so that the valve remains
at that particular opening.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
Description
EC-422

CONSULT-II Reference Value in Data Monitor
Mode
NBEC0250Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
IACV-AAC/VIEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 14 - 20 step
2,000 rpm Ð
ECM Terminals and Reference ValueNBEC0670Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
6
7
8
17PU/G
GY
Y
GY/LIACV-AAC valve[Engine is running]
IIdle speed0.1 - 14V
On Board Diagnosis LogicNBEC0252Malfunction is detected when
(Malfunction A)the IACV-AAC valve does not operate properly,
(Malfunction B)the IACV-AAC valve does not operate properly.
Possible CauseNBEC0515MALFUNCTION ANBEC0515S01IHarness or connectors
(The IACV-AAC valve circuit is open.)
IIACV-AAC valve
MALFUNCTION BNBEC0515S02IHarness or connectors
(The IACV-AAC valve circuit is shorted.)
IAir control valve (Power steering)
IIACV-AAC valve
DTC Confirmation ProcedureNBEC0253NOTE:
IIf ªDTC Confirmation Procedureº has been previously
conducted, always turn ignition switch ªOFFº and wait at least
10 seconds before conducting the next test.
IPerform ªPROCEDURE FOR MALFUNCTION Aº first. If 1st
trip DTC cannot be confirmed, perform ªPROCEDURE
FOR MALFUNCTION Bº.
GI
MA
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LC
FE
AT
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PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
CONSULT-II Reference Value in Data Monitor Mode
EC-423

3 CHECK IACV-AAC VALVE OUTPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminals and IACV-AAC valve terminals as follows.
Refer to Wiring Diagram.
MTBL0354
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F101, F6
IHarness for open or short between IACV-AAC valve and ECM
©Repair harness connectors.
5 CHECK AIR CONTROL VALVE (POWER STEERING) OPERATION-I
1. Reconnect ECM harness connector and IACV-AAC valve harness connector.
2. Disconnect vacuum hose connected to air control valve (Power steering) at intake air duct.
3. Start engine and let it idle.
4. Check vacuum hose for vacuum existence.
SEF995Y
Vacuum slightly exists or does not exist.
OK or NG
OK©GO TO 6.
NG©Replace air control valve (Power steering).
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
Diagnostic Procedure (Cont'd)
EC-427

6 CHECK AIR CONTROL VALVE (POWER STEERING) OPERATION-II
Check vacuum hose for vacuum existence when steering wheel is turned.
SEF995Y
Vacuum should exist.
OK or NG
OK©GO TO 9.
NG©GO TO 7.
7 CHECK VACUUM PORT
1. Stop engine.
2. Disconnect vacuum hose connected to air control valve (Power steering) at vacuum port.
3. Blow air into vacuum port.
4. Check that air flows freely.
SEF996Y
OK or NG
OK©GO TO 8.
NG©Repair or clean vacuum port.
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
Diagnostic Procedure (Cont'd)
EC-428

8 CHECK VACUUM HOSES AND TUBES
1. Disconnect vacuum hoses between air control valve (Power steering) and vacuum port, air control valve (Power steer-
ing) and intake air duct.
2. Check the hoses and tubes for crack, clogging, improper connection or disconnection.
SEF109L
OK or NG
OK©GO TO 9.
NG©Repair hoses or tubes.
9 CHECK IACV-AAC VALVE-I
1. Disconnect IACV-AAC valve harness connector.
2. Check resistance between IACV-AAC valve terminal 2 and terminals 1, 3, terminal 5 and terminals 4, 6.
SEF344XA
OK or NG
OK©GO TO 10.
NG©Replace IACV-AAC valve assembly.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0505 IDLE AIR CONTROL VALVE (IACV) Ð AUXILIARY AIR CONTROL
(AAC) VALVE
Diagnostic Procedure (Cont'd)
EC-429

SEF028Z
Component DescriptionNBEC0398The power steering oil pressure switch is attached to the power
steering high-pressure tube and detects a power steering load.
When a power steering load is detected, it signals the ECM. The
ECM adjusts the IACV-AAC valve to increase the idle speed and
adjust for the increased load.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0399Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
PW/ST SIGNALIEngine: After warming up, idle
the engineSteering wheel in neutral position
(forward direction)OFF
The steering wheel is fully turned. ON
ECM Terminals and Reference ValueNBEC0687Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
47 R/BPower steering oil
pressure switch[Engine is running]
ISteering wheel is being turned.0 - 1.0V
[Engine is running]
ISteering wheel is not being turned.Approximately 5V
POWER STEERING OIL PRESSURE SWITCH
Component Description
EC-634

Wiring DiagramNBEC0401
MEC977C
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
POWER STEERING OIL PRESSURE SWITCH
Wiring Diagram
EC-635