2001 INFINITI QX4 Fuel

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
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
FUEL PUMP
System Description
EC-625

ECM Terminals and Reference Value=NBEC0686Specification 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)
28 R/L Fuel pump relay[Ignition switch ªONº]
IFor 1 second after turning ignition switch ªONº
[Engine is running]0 - 1.5V
[Ignition switch ªONº]
I1 second passed after turning ignition switch
ªONº.BATTERY VOLTAGE
(11 - 14V)
FUEL PUMP
ECM Terminals and Reference Value
EC-626

Wiring DiagramNBEC0396
MEC976C
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
FUEL PUMP
Wiring Diagram
EC-627

Diagnostic ProcedureNBEC0397
1 CHECK OVERALL FUNCTION
1. Turn ignition switch ªONº.
2. Pinch fuel feed hose with two fingers.
SEF025Z
Fuel pressure pulsation should be felt on the fuel feed hose for 1 second after ignition switch is turned ªONº.
OK or NG
OK©INSPECTION END
NG©GO TO 2.
2 CHECK FUEL PUMP RELAY-1 and -2 POWER SUPPLY CIRCUIT-I
1. Turn ignition switch ªOFFº.
2. Disconnect fuel pump relay-1 and -2.
SEF346Z
3. Turn ignition switch ªONº.
4. Check voltage between terminals 2 and ground with CONSULT-II or tester.
SEF347Z
OK or NG
OK©GO TO 4.
NG©GO TO 3.
FUEL PUMP
Diagnostic Procedure
EC-628

3 DETECT MALFUNCTIONING PART
Check the following.
IFuse block (J/B) connector M10
I15A fuse in fuse block (J/B)
IHarness connectors M1, E1
IHarness for open or short between fuse and fuel pump relay-1 and fuel pump relay-2
©Repair harness or connectors.
4 CHECK FUEL PUMP RELAY-1 POWER SUPPLY CIRCUIT-II
Check voltage between terminal 3 and ground with CONSULT-II or tester.
SEF348Z
OK or NG
OK©GO TO 8.
NG©GO TO 5.
5 CHECK FUEL PUMP RELAY-2 OUTPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect fuel pump relay-2.
2. Check harness continuity between fuel pump relay-2 terminal 5 and fuel pump relay-1 terminal 3. 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 6.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
FUEL PUMP
Diagnostic Procedure (Cont'd)
EC-629

6 CHECK FUEL PUMP RELAY POWER SUPPLY CIRCUIT-III
1. Turn ignition switch ªOFFº.
2. Disconnect fuel pump relay-2.
3. Turn ignition switch ªONº.
4. Check voltage between terminals 2, 3 and ground with CONSULT-II or tester.
SEF026Z
OK or NG
OK©GO TO 8.
NG©GO TO 7.
7 DETECT MALFUNCTIONING PART
Check the following.
I15A fuse in fusible link and relay box
IHarness for open or short between fuse and fuel pump relay-2
©Repair harness or connectors.
8 CHECK FUEL PUMP RELAY-2 GROUND CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between fuel pump relay-2 terminal 1 and ground.
Continuity should exist.
2. Also check harness for short to power.
OK or NG
©Repair open circuit or short to power in harness or connector.
FUEL PUMP
Diagnostic Procedure (Cont'd)
EC-630

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.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
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