2001 INFINITI QX4 02 sensor

DescriptionNBEC0596SYSTEM DESCRIPTIONNBEC0596S01
Sensor Input Signal to ECMECM func-
tionActuator
Mass air flow sensor Amount of intake air
VIAS con-
trolVIAS control solenoid valve Throttle position sensor Throttle position
Closed throttle position Throttle valve idle position
Ignition switch Start signal
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
Engine coolant temperature sensor Engine coolant temperature
SEF447Z
When the engine is running at low or medium speed, the power
valve is fully closed. Under this condition, the effective suction port
length is equivalent to the total length of the intake manifold collec-
tor's suction port including the intake valve. This long suction port
provides increased air intake which results in improved suction
efficiency and higher torque generation.
The surge tank and one-way valve are provided. When engine is
running at high speed, the ECM sends the signal to the VIAS con-
trol solenoid valve. This signal introduces the intake manifold
vacuum into the power valve actuator and therefore opens the
power valve to two suction passages together in the collector.
Under this condition, the effective port length is equivalent to the
length of the suction port provided independently for each cylinder.
This shortened port length results in enhanced engine output with
reduced suction resistance under high speeds.
VARIABLE INDUCTION AIR CONTROL SYSTEM (VIAS)
Description
EC-610

System DescriptionNBEC0392
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed (POS signal)
Fuel pump
controlFuel pump relay Crankshaft position sensor (REF) Engine speed (REF signal)
Ignition switch Start signal
The ECM activates the fuel pump for several seconds after the ignition switch is turned on to improve engine
startability. If the ECM receives a 120É signal from the crankshaft position sensor (REF), it knows that the
engine is rotating, and causes the pump to operate. If the 120É signal is not received when the ignition switch
is on, the engine stalls. The ECM stops pump operation and prevents battery discharging, thereby improving
safety. The ECM does not directly drive the fuel pump. It controls the ON/OFF fuel pump relay, which in turn
controls the fuel pump.
Condition Fuel pump operation
Ignition switch is turned to ON. Operates for 1 second.
Engine running and cranking Operates.
When engine is stopped Stops in 1.5 seconds.
Except as shown aboveStops.
SEF018S
Component DescriptionNBEC0393The fuel pump with a fuel damper is an in-tank type (the pump and
damper are located in the fuel tank).
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0394Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
FUEL PUMP RLYIIgnition switch is turned to ON. (Operates for 1 second.)
IEngine running and crankingON
Except as shown above OFF
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FUEL PUMP
System Description
EC-625

9 CHECK FUEL PUMP POWER SUPPLY AND GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect fuel level sensor unit and fuel pump harness connector.
SEF021S
3. Check harness continuity between fuel pump terminal 2 and body ground, fuel pump terminal 1 and fuel pump relay-1
terminal 5. Refer to Wiring Diagram.
Continuity should exist.
4. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 11.
NG©GO TO 10.
10 DETECT MALFUNCTIONING PART
Check harness for open or short between fuel pump relay and fuel pump.
©Repair open circuit or short to ground or short to power in harness or connectors.
11 CHECK FUEL PUMP RELAY OUTPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal 28 and fuel pump relay-1 terminal 1. Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 13.
NG©GO TO 12.
12 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1
IHarness connectors M32, F23
IHarness for open or short between ECM and fuel pump relay-1
©Repair open circuit or short to ground or short to power in harness or connectors.
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FUEL PUMP
Diagnostic Procedure (Cont'd)
EC-631

13 CHECK FUEL PUMP RELAY-1 AND -2
With CONSULT-II
1. Reconnect fuel pump relay-1 and -2, fuel level sensor unit and fuel pump harness connector and ECM harness con-
nector.
2. Turn ignition switch ªONº.
3. Turn fuel pump relay-1, -2 ªONº and ªOFFº in ªACTIVE TESTº mode with CONSULT-II and check operating sound.
SEF073Y
Without CONSULT-II
Check continuity between terminals 3 and 5 under the following conditions.
SEF608X
OK or NG
OK©GO TO 14.
NG©Replace fuel pump relay.
14 CHECK FUEL PUMP
1. Disconnect fuel level sensor unit and fuel pump harness connector.
2. Check resistance between fuel level sensor unit and fuel pump terminals 1 and 2.
SEF027Z
OK or NG
OK©GO TO 15.
NG©Replace fuel pump.
FUEL PUMP
Diagnostic Procedure (Cont'd)
EC-632

SEF029Z
DescriptionNBEC0636The refrigerant pressure sensor is installed at the liquid tank of the
air conditioner system. The sensor uses an electrostatic volume
pressure transducer to convert refrigerant pressure to voltage. The
voltage signal is sent to ECM, and ECM controls cooling fan sys-
tem.
SEF099XA
ECM Terminals and Reference ValueNBEC0689Specification 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)
58 B/P Sensors' ground[Engine is running]
IWarm-up condition
IIdle speedApproximately 0V
81 W/PURefrigerant pressure
sensor[Engine is running]
IWarm-up condition
IBoth A/C switch and blower switch are ªONº.
(Compressor operates.)1.0 - 4.0V
111 P/B Sensors' power supply[Ignition switch ªONº]Approximately 5V
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REFRIGERANT PRESSURE SENSOR
Description
EC-639

Wiring DiagramNBEC0637
MEC982C
REFRIGERANT PRESSURE SENSOR
Wiring Diagram
EC-640

Diagnostic ProcedureNBEC0638
1 CHECK REFRIGERANT PRESSURE SENSOR OVERALL FUNCTION
1. Start engine and warm it up to normal operating temperature.
2. Turn A/C switch and blower switch ªONº.
3. Check voltage between ECM terminal 81 and ground with CONSULT-II or tester.
SEF617XA
OK or NG
OK©INSPECTION END
NG©GO TO 2.
2 CHECK REFRIGERANT PRESSURE SENSOR POWER SUPPLY CIRCUIT
1. Turn A/C switch and blower switch ªOFFº.
2. Stop engine.
3. Disconnect refrigerant pressure sensor harness connector.
SEF029Z
4. Turn ignition switch ªONº.
5. Check voltage between refrigerant pressure sensor terminal 1 and ground with CONSULT-II or tester.
SEF030Z
OK or NG
OK©GO TO 4.
NG©GO TO 3.
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REFRIGERANT PRESSURE SENSOR
Diagnostic Procedure
EC-641

3 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1
IHarness for open or short between ECM and refrigerant pressure sensor
©Repair harness or connectors.
4 CHECK REFRIGERANT PRESSURE SENSOR GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Check harness continuity between refrigerant pressure sensor terminal 1 and engine ground. Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to power.
OK or NG
OK©GO TO 6.
NG©GO TO 5.
5 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1 and M33, F22
IHarness connectors F23, M32
IHarness for open between ECM and refrigerant pressure sensor
IHarness for open between TCM (Transmission control module) and refrigerant pressure sensor
©Repair open circuit or short to power in harness or connectors.
6 CHECK REFRIGERANT PRESSURE SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal 81 and refrigerant pressure sensor terminal 2. Refer to Wiring Dia-
gram.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 8.
NG©GO TO 7.
7 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors E1, M1 and M94, F27
IHarness for open or short between ECM and refrigerant pressure sensor
©Repair open circuit or short to ground or short to power in harness or connectors.
8 CHECK REFRIGERANT PRESSURE SENSOR
Refer to HA-14, ªRefrigerant pressure sensorº.
OK or NG
OK©GO TO 9.
NG©Replace refrigerant pressure sensor.
9 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
REFRIGERANT PRESSURE SENSOR
Diagnostic Procedure (Cont'd)
EC-642