Nissan Pathfinder. Manual — part 487
EC-254
< DTC/CIRCUIT DIAGNOSIS >
[VQ35DE]
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
1. Start engine.
2. Perform “POWER BALANCE” in “ACTIVE TEST” mode with CONSULT.
3. Check that each circuit produces a momentary engine speed drop.
With GST
1. Let engine idle.
2. Listen to each fuel injector operating sound.
Is the inspection result normal?
YES
>> GO TO 8.
NO
>> Perform trouble diagnosis for FUEL INJECTOR, refer to
.
8.
CHECK FUEL INJECTOR
1. Turn ignition switch OFF.
2. Confirm that the engine is cooled down and there are no fire hazards near the vehicle.
3. Disconnect all fuel injector harness connectors.
4. Remove fuel tube assembly. Refer to
EM-47, "Removal and Installation"
.
Keep fuel hose and all fuel injectors connected to fuel tube.
5. For DTC P0171, reconnect fuel injector harness connectors on bank 1.
For DTC P0174, reconnect fuel injector harness connectors on bank 2.
6. Disconnect all ignition coil harness connectors.
7. Prepare pans or saucers under each fuel injector.
8. Crank engine for about 3 seconds.
For DTC P0171, check that fuel sprays out from fuel injectors on bank 1.
For DTC P0174, check that fuel sprays out from fuel injectors on bank 2.
Is the inspection result normal?
YES
>> Check intermittent incident. Refer to
GI-49, "Intermittent Incident"
.
NO
>> Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.
EM-47, "Removal and Installation"
.
PBIB3332E
Fuel should be sprayed evenly for each fuel injector.
P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
EC-255
< DTC/CIRCUIT DIAGNOSIS >
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P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
DTC Logic
INFOID:0000000009178170
DTC DETECTION LOGIC
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from A/F sensor 1. The ECM calculates
the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (the actual mixture ratio is too rich), the ECM
judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).
DTC CONFIRMATION PROCEDURE
1.
PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-
ing the next test.
1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
>> GO TO 2.
2.
PERFORM DTC CONFIRMATION PROCEDURE-I
1. Clear the mixture ratio self-learning value. Refer to
.
2. Start engine.
Is it difficult to start engine?
YES
>> GO TO 3.
NO
>> GO TO 4.
3.
RESTART ENGINE
If it is difficult to start engine, the fuel injection system has a malfunction, too.
Crank engine while depressing accelerator pedal.
NOTE:
• When depressing accelerator pedal three-fourths (3/4) or more, the control system does not start the
engine. Do not depress accelerator pedal too much.
Does engine start?
YES
>> Proceed to
.
NO
>> Check exhaust and intake air leakage visually.
4.
PERFORM DTC CONFIRMATION PROCEDURE-II
1. Keep engine idle for at least 5 minutes.
2. Check 1st trip DTC.
Is 1st trip DTC detected?
YES
>> Proceed to
.
NO
>> GO TO 5.
Sensor
Input signal to ECM
ECM function
Actuator
A/F sensor 1
Density of oxygen in exhaust gas
(Mixture ratio feedback signal)
Fuel injection control
Fuel injector
DTC No.
CONSULT screen terms
(Trouble diagnosis content)
DTC detecting condition
Possible cause
P0172
FUEL SYS-RICH-B1
(System too rich bank 1)
• Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too
large. (The mixture ratio is too rich.)
• A/F sensor 1
• Fuel injector
• Exhaust gas leakage
• Incorrect fuel pressure
• Mass air flow sensor
P0175
FUEL SYS-RICH-B2
(System too rich bank 2)
EC-256
< DTC/CIRCUIT DIAGNOSIS >
[VQ35DE]
P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
5.
PERFORM DTC CONFIRMATION PROCEDURE-III
1. Turn ignition switch OFF and wait at least 10 seconds.
2. Start engine.
3. Maintain the following conditions for at least 10 consecutive minutes.
Hold the accelerator pedal as steady as possible.
CAUTION:
Always drive vehicle at a safe speed.
4. Check 1st trip DTC.
Is 1st trip DTC detected?
YES
>> Proceed to
.
NO
>> INSPECTION END
Diagnosis Procedure
INFOID:0000000009178171
1.
CHECK EXHAUST GAS LEAKAGE
1. Start engine and run it at idle.
2. Listen for an exhaust gas leakage before three way catalyst (manifold).
Is exhaust gas leakage detected?
YES
>> Repair or replace malfunctioning part.
NO
>> GO TO 2.
2.
CHECK FOR INTAKE AIR LEAKAGE
Listen for an intake air leakage after the mass air flow sensor.
Is intake air leakage detected?
YES
>> Repair or replace malfunctioning part.
NO
>> GO TO 3.
3.
CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT
1. Turn ignition switch OFF.
2. Disconnect corresponding A/F sensor 1 harness connector.
3. Disconnect ECM harness connector.
4. Check the continuity between A/F sensor 1 harness connector and ECM harness connector.
5. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector
and ground.
VHCL SPEED SE
50 - 120 km/h (31 - 75 mph)
PBIB1216E
DTC
A/F sensor 1
ECM
Continuity
Bank
Connector
Terminal
Connector
Terminal
P0172
1
F5
1
F52
69
Existed
2
73
P0175
2
F65
1
77
2
81
P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
EC-257
< DTC/CIRCUIT DIAGNOSIS >
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6. Also check harness for short to power.
Is the inspection result normal?
YES
>> GO TO 4.
NO
>> Repair open circuit, short to ground or short to power in harness or connectors.
4.
CHECK FUEL PRESSURE
1. Release fuel pressure to zero. Refer to
.
2. Install fuel pressure gauge kit [SST: — (J-44321)] and check fuel pressure. Refer to
Is the inspection result normal?
YES
>> GO TO 5.
NO
>> Replace “fuel filter and fuel pump assembly”. Refer to
FL-6, "Removal and Installation"
.
5.
CHECK MASS AIR FLOW SENSOR
With CONSULT
1. Install all removed parts.
2. Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT.
For specification, refer to
EC-467, "Mass Air Flow Sensor"
With GST
1. Install all removed parts.
2. Check mass air flow sensor signal in “Service $01” with GST.
For specification, refer to
EC-467, "Mass Air Flow Sensor"
Is the measurement value within the specification?
YES
>> GO TO 6.
NO
>> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or
ground. Refer to
6.
CHECK FUNCTION OF FUEL INJECTOR
With CONSULT
1. Start engine.
2. Perform “POWER BALANCE” in “ACTIVE TEST” mode with CONSULT.
3. Check that each circuit produces a momentary engine speed drop.
With GST
1. Let engine idle.
DTC
A/F sensor 1
Ground
Continuity
Bank
Connector
Terminal
P0172
1
F5
1
Ground
Not existed
2
P0175
2
F65
1
2
DTC
ECM
Ground
Continuity
Connector
Terminal
P0172
F52
69
Ground
Not existed
73
P0175
77
81
At idling: Approximately 350 kPa (3.57 kg/cm
2
, 51 psi)
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