Nissan Altima (L32) 2007-2012 Service Manual: P0172, P0175 Fuel injection system function

DTC Logic

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 conducting 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 EC-1055, "MIXTURE RATIO SELF-LEARNING VALUE CLEAR : Special Repair Requirement".

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 >> Go to EC-1271, "Diagnosis Procedure".

NO >> Remove spark plugs and check for fouling, etc.

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 >> Go to EC-1271, "Diagnosis Procedure".

NO >> GO TO 5.

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 >> Go to EC-1271, "Diagnosis Procedure".

NO >> INSPECTION END

Diagnosis Procedure

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.

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 EC-1579, "Inspection".

2. Install fuel pressure gauge kit [SST (J-44321)] and check fuel pressure. Refer to EC-1579, "Inspection".

At idling: Approximately 350 kPa (3.57 kg/cm2, 51 psi)

Is the inspection result normal? YES >> GO TO 5.

NO >> Replace “fuel filter and fuel pump assembly”.

5.CHECK MASS AIR FLOW SENSOR

1. Install all removed parts.

2. Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT-III.

For specification, refer to EC-1585, "Mass Air Flow Sensor".

1. Install all removed parts.

2. Check mass air flow sensor signal in “Service $01” with GST.

For specification, refer to EC-1585, "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 EC-1202, "Diagnosis Procedure".

6.CHECK FUNCTION OF FUEL INJECTOR

1. Start engine.

2. Perform “POWER BALANCE” in “ACTIVE TEST” mode with CONSULT-III.

3. Check that each circuit produces a momentary engine speed drop.

1. Let engine idle.

2. Listen to each fuel injector operating sound.

Is the inspection result normal? YES >> GO TO 7.

NO >> Perform trouble diagnosis for FUEL INJECTOR, refer to EC-1483, "Diagnosis Procedure".

7.CHECK FUEL INJECTOR

1. Remove fuel injector assembly. Refer to EM-146, "Removal and Installation".

Keep fuel hose and all fuel injectors connected to fuel tube.

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. Disconnect all ignition coil harness connectors.

5. Prepare pans or saucers under each fuel injector.

6. Crank engine for approximately 3 seconds.

Check that fuel does not drip from fuel injector.

Is the inspection result normal? YES >> GO TO 8.

NO >> Replace the fuel injectors from which fuel is dripping. Always replace O-ring with new one.

8.CHECK INTERMITTENT INCIDENT

Refer to GI-42, "Intermittent Incident".

>> INSPECTION END