P0171, P0174 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 lean), the
ECM judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).

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 See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Programming and Relearning\Mixture Ratio Self-Learning Value Clear\Description See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Programming and Relearning\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 Diagnosis Procedure.
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 >> Go to 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.

4. Check 1st trip DTC. Is 1st trip DTC detected?

YES >> Go to 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).

1. Listen for an intake air leakage after the mass air flow sensor.
2. Check PCV hose connection. 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 See: Engine, Cooling and Exhaust\Engine\Fuel Pressure\Testing and Inspection.
2. Install fuel pressure gauge kit [SST (J-44321)] and check fuel pressure. Refer to See: Engine, Cooling and Exhaust\Engine\Fuel Pressure\Testing and Inspection.

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

Is the Inspection result normal?
YES >> GO TO 6.
NO >> GO TO 5.

5. DETECT MALFUNCTIONING PART Check fuel hoses and fuel tubes for clogging.

Is the Inspection result normal?
YES >> Replace "fuel filter and fuel pump assembly".
NO >> Repair or replace malfunctioning part.
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. For specification, refer to See: Powertrain Management\Computers and Control Systems\Air Flow Meter/Sensor\Specifications.

With GST

1. Install all removed parts.
2. Check mass air flow sensor signal in Service $01 with GST. For specification, refer to See: Powertrain Management\Computers and Control Systems\Air Flow Meter/Sensor\Specifications.

Is the measurement value within the specification?
YES >> GO TO 7.
NO >> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to See: P0102.
7.CHECK FUNCTION OF FUEL INJECTOR
With CONSULT-III

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. 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 See: Powertrain Management\Fuel Delivery and Air Induction\Testing and Inspection\Component Tests and General Diagnostics\Fuel Injector\Diagnosis Procedure.
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 See: Powertrain Management\Fuel Delivery and Air Induction\Fuel Rail\Service and Repair. 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 approximately 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.

Fuel should be sprayed evenly for each fuel injector.

Is the Inspection result normal?
YES >> GO TO 9.
NO >> Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.
9.CHECK INTERMITTENT INCIDENT
Refer to See: Testing and Inspection\Initial Inspection and Diagnostic Overview\Service Information For Electrical Incident\Intermittent Incident.
>> Inspection END