Infiniti QX56 (JA60). Manual — part 380
EC-172
< COMPONENT DIAGNOSIS >
[VK56DE]
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
On Board Diagnosis Logic
INFOID:0000000005149190
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 the A/F sensors 1. The ECM calcu-
lates 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 lean.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).
DTC Confirmation Procedure
INFOID:0000000005149191
NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure
before conducting the next step.
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.
WITH CONSULT-III
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Turn ignition switch ON and select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CON-
SULT-III.
6. Clear the self-learning control coefficient by touching “CLEAR”.
7. Start engine.
If it is difficult to start engine, the fuel injection system has a malfunction.
Performing the following procedure is advised.
a. 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.
b. If engine starts, go to
.
If engine does not start, check exhaust and intake air leakage visually.
8. Keep engine at idle for least 5 minutes.
9. Check 1st trip DTC.
10. The 1st trip DTC P0171 or P0174 should be detected at this stage, if a malfunction exists. If so, go to
NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.
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.
Trouble diagnosis name
DTC detecting condition
Possible cause
P0171
0171
(Bank 1)
Fuel injection system too
lean
• Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too
large. (The mixture ratio is too lean.)
• Intake air leaks
• A/F sensor 1
• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor
• Incorrect PCV hose connection
P0174
0174
(Bank 2)
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-173
< COMPONENT DIAGNOSIS >
[VK56DE]
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a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine.
c. 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.
d. Check 1st trip DTC.
e. If 1st trip DTC is detected, go to
WITH GST
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Disconnect mass air flow sensor harness connector.
6. Restart engine and let it idle for at least 5 seconds.
7. Stop engine and reconnect mass air flow sensor harness con-
nector.
8. Select Service $03 with GST. Make sure DTC P0102 is
detected.
9. Select Service $04 with GST and erase the DTC P0102.
10. Start engine.
If it is difficult to start engine, the fuel injection system has a mal-
function.
Performing the following procedure is advised.
a. 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.
b. If engine starts, go to
.
If engine does not start, check exhaust and intake air leakage visually.
11. Keep engine at idle for at least 5 minutes.
12. Check 1st trip DTC.
13. The 1st trip DTC P0171 or P0174 should be detected at this stage, if a malfunction exists. If so, go to
NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine.
c. 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.
d. Check 1st trip DTC.
e. If 1st trip DTC is detected, go to
Diagnosis Procedure
INFOID:0000000005149192
1.
CHECK EXHAUST GAS LEAK
VHCL SPEED SE
50 - 120 km/h (31 - 75 MPH)
VHCL SPEED SE
50 - 120 km/h (31 - 75 MPH)
BBIA0368E
EC-174
< COMPONENT DIAGNOSIS >
[VK56DE]
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
1. Start engine and run it at idle.
2. Listen for an exhaust gas leak before three way catalyst (manifold).
OK or NG
OK
>> GO TO 2.
NG
>> Repair or replace.
2.
CHECK FOR INTAKE AIR LEAK
1. Listen for an intake air leak after the mass air flow sensor.
2. Check PCV hose connection.
OK or NG
OK
>> GO TO 3.
NG
>> Repair or replace.
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 harness continuity between the following terminals.
Refer to Wiring Diagram.
5. Check harness continuity between the following terminals and ground.
Refer to Wiring Diagram.
PBIB1216E
A/F sensor 1 terminal
ECM terminal
Bank 1
1
35
2
56
Bank 2
1
16
2
75
Continuity should exist.
Bank 1
Bank 2
A/F sensor 1 terminal
ECM terminal
A/F sensor 1 terminal
ECM terminal
1
35
1
16
2
56
2
75
BBIA0376E
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-175
< COMPONENT DIAGNOSIS >
[VK56DE]
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6. Also check harness for short to power.
OK or NG
OK
>> GO TO 4.
NG
>> Repair open circuit or 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
.
OK or NG
OK
>> GO TO 6.
NG
>> GO TO 5.
5.
DETECT MALFUNCTIONING PART
Check the following.
• Fuel pump and circuit (Refer to
• Fuel pressure regulator (Refer to
• Fuel lines
• Fuel filter for clogging
>> Repair or replace.
6.
CHECK MASS AIR FLOW SENSOR
With CONSULT-III
1. Install all removed parts.
2. Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT-III.
With GST
1. Install all removed parts.
2. Check mass air flow sensor signal in Service $01 with GST.
OK or NG
OK
>> GO TO 7.
NG
>> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or
grounds. Refer to
.
7.
CHECK FUNCTION OF FUEL INJECTOR
With CONSULT-III
1. Start engine.
2. Perform “POWER BALANCE” in “ACTIVE TEST” mode with CONSULT-III.
3. Make sure that each circuit produces a momentary engine speed drop.
Without CONSULT-III
1. Start engine.
Continuity should not exist.
At idling: Approximately 350 kPa (3.57 kg/cm
2
, 51 psi)
3.0 - 9.0 g·m/sec:
at idling
9.0 - 28.0 g·m/sec:
at 2,500 rpm
3.0 - 9.0 g·m/sec:
at idling
9.0 - 28.0 g·m/sec:
at 2,500 rpm
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