2001 INFINITI QX4 P0171

4 CHECK FUEL PRESSURE
1. Release fuel pressure to zero. Refer to EC-39.
2. Install fuel pressure gauge and check fuel pressure. Refer to EC-39.
At idling:
When fuel pressure regulator valve vacuum hose is connected.
235 kPa (2.4 kg/cm
2, 34 psi)
When fuel pressure regulator valve vacuum hose is disconnected.
294 kPa (3.0 kg/cm
2, 43 psi)
OK or NG
OK©GO TO 6.
NG©GO TO 5.
5 DETECT MALFUNCTIONING PART
Check the following.
IFuel pump and circuit (Refer to EC-625.)
IFuel pressure regulator (Refer to EC-40.)
IFuel lines (Refer to MA-16, ªChecking Fuel Linesº.)
IFuel filter for clogging
©Repair or replace.
6 CHECK MASS AIR FLOW SENSOR
With CONSULT-II
1. Install all removed parts.
2. Check ªMASS AIR FLOWº in ªDATA MONITORº mode with CONSULT-II.
2.0 - 6.0 g´m/sec: at idling
7.0 - 20.0 g´m/sec: at 2,500 rpm
With GST
1. Install all removed parts.
2. Check mass air flow sensor signal in MODE 1 with GST.
2.0 - 6.0 g´m/sec: at idling
7.0 - 20.0 g´m/sec: at 2,500 rpm
OK or NG
OK©GO TO 7.
NG©Check connectors for rusted terminals or loose connections in the mass air flow sensor
circuit or engine grounds. Refer to EC-150.
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
Diagnostic Procedure (Cont'd)
EC-299

7 CHECK FUNCTION OF INJECTORS
With CONSULT-II
1. Start engine.
2. Perform ªPOWER BALANCEº in ªACTIVE TESTº mode with CONSULT-II.
SEF070Y
3. Make sure that each circuit produces a momentary engine speed drop.
Without CONSULT-II
1. Start engine.
2. Listen to each injector operating sound.
MEC703B
Clicking noise should be heard.
OK or NG
OK©GO TO 8.
NG©Perform trouble diagnosis for ªINJECTORSº, EC-616.
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
Diagnostic Procedure (Cont'd)
EC-300

8 CHECK INJECTOR
1. Confirm that the engine is cooled down and there are no fire hazards near the vehicle.
2. Turn ignition switch ªOFFº.
3. Disconnect injector harness connectors on left bank (for DTC P0171), right bank (for DTC P0174).
4. Remove injector gallery assembly. Refer to EC-41.
Keep fuel hose and all injectors connected to injector gallery.
The injector harness connectors on right bank (for DTC P0171), left bank (for DTC P0174) should remain connected.
5. Disconnect all ignition coil harness connectors.
6. Prepare pans or saucers under each injector.
7. Crank engine for about 3 seconds. Make sure that fuel sprays out from injectors.
SEF595Q
Fuel should be sprayed evenly for each injector.
OK or NG
OK©GO TO 9.
NG©Replace injectors from which fuel does not spray out. Always replace O-ring with new
ones.
9 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
Diagnostic Procedure (Cont'd)
EC-301