P0174

DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

On Board Diagnosis 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 the A/F sensors 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 lights up the MIL (2 trip detection logic).

DTC Confirmation Procedure

NOTE:
If DTC Confirmation Procedure has been previously conducted, always perform the following 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 CONSULT-III.
6. Clear the self-learning control coefficient by touching "CLEAR".
7. Select "DATA MONITOR" mode with CONSULT-III.
8. Start engine again and let it idle for at least 5 minutes.
The 1st trip DTC P0171 or P0174 should be detected at this stage, if a malfunction exists. If so, go to "Diagnosis Procedure".

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.

WARNING:
Always drive vehicle at a safe speed.
9. If it is difficult to start engine at step 6, the fuel injection system has a malfunction, too.
10. Crank engine while depressing accelerator pedal. If engine starts, go to "Diagnosis Procedure". If engine does not start, check exhaust and intake air leak visually.

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 connector.
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 again and let it idle for at least 10 minutes.
11. Select Service $07 with GST. The 1st trip DTC P0171 or P0174 should be detected at this stage, if a malfunction exists. If so, go to "Diagnosis Procedure".

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.

WARNING:
Always drive vehicle at a safe speed.
12. If it is difficult to start engine at step 8, the fuel injection system has a malfunction.
13. Crank engine while depressing accelerator pedal. If engine starts, go to "Diagnosis Procedure".
If engine does not start, check exhaust and intake air leak visually.

Wiring Diagram

BANK 1

EC-FUELB1-01:

Specification data are reference values and are measured between each terminal and ground.
Pulse signal is measured by CONSULT-III.

CAUTION:
Never use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.

BANK 2

EC-FUELB2-01:

Diagnosis Procedure
1.CHECK EXHAUST GAS LEAK
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.

Continuity should exist.

5. Check harness continuity between the following terminals and ground. Refer to Wiring Diagram.

Continuity should not exist.

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 Testing and Inspection.
2. Install fuel pressure gauge and check fuel pressure. Refer to Testing and Inspection.

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

OK or NG
OK (With CONSULT-III)-GO TO 6.
OK (Without CONSULT-III)-GO TO 7.
NG - GO TO 5.
5.DETECT MALFUNCTIONING PART
Check the following.
- Fuel pump and circuit (Refer to Fuel Pump Fuel Pump.)
- Fuel pressure regulator (Refer to Testing and Inspection.)
- 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.

OK or NG
OK - GO TO 8.
NG - Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to P0101.
7.CHECK MASS AIR FLOW SENSOR
With GST
1. Install all removed parts.
2. Check mass air flow sensor signal in Service $01 with GST.

OK or NG
OK (P0171)-GO TO 9.
OK (P0174)-GO TO 11.
NG - Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to P0101 .
8.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.
OK or NG
OK - GO TO 12.
NG - Perform trouble diagnosis for FUEL INJECTOR, refer to Component Description Fuel Injector.
9.CHECK FUNCTION OF FUEL INJECTOR-I
Without CONSULT-III
1. Stop engine.

2. Disconnect harness connector F44 (2), F101 (3)
3. Turn ignition switch ON.
- Arrow indicates vehicle front
- Intake manifold collector (1)

4. Check voltage between harness connector F44 terminal 5 and ground with CONSULT-III or tester.

Voltage: Battery voltage

5. Turn ignition switch OFF.
6. Disconnect ECM harness connector.
7. Check harness continuity between harness connector F44 terminal and ECM terminal as follows. Refer to Wiring Diagram.

Continuity should exist.

8. Also check harness for short to ground and short to power.
OK or NG
OK - GO TO 10.
NG - Perform trouble diagnosis for FUEL INJECTOR, refer to Component Description Fuel Injector.
10.CHECK FUNCTION OF FUEL INJECTOR-II

Provide battery voltage between harness connector F101 as follows and then interrupt it. Listen to each fuel injector operating sound.

Operating sound should exist.

OK or NG
OK - GO TO 12.
NG - Perform trouble diagnosis for FUEL INJECTOR, refer to Component Description Fuel Injector.
11.CHECK FUNCTION OF FUEL INJECTOR

1. Start engine.
2. Listen to fuel injectors No.2, No.4, No.6 operating sound.

Clicking noise should exist.

OK or NG
OK - GO TO 12.
NG - Perform trouble diagnosis for FUEL INJECTOR, refer to Component Description, Fuel Injector.
12.CHECK FUEL INJECTOR
1. Confirm that the engine is cooled down and there are no fire hazards near the vehicle.
2. Turn ignition switch OFF.
3. Reconnect all harness connectors disconnected.
4. Disconnect all fuel injector harness connectors.
5. Remove fuel tube assembly. Refer to Service and Repair.
Keep fuel hose and all fuel injectors connected to fuel tube.
6. For DTC P0171, reconnect fuel injector harness connectors on bank 1.
For DTC P0174, reconnect fuel injector harness connectors on bank 2.
7. Disconnect all ignition coil harness connectors.
8. Prepare pans or saucers under each fuel injector.

9. Crank engine for about 3 seconds.
For DTC P0171, make sure that fuel sprays out from fuel injectors on bank 1.
For DTC P0174, make sure that fuel sprays out from fuel injectors on bank 2.

Fuel should be sprayed evenly for each fuel injector.

OK or NG
OK - GO TO 13.
NG - Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.
13.CHECK INTERMITTENT INCIDENT
Refer to Description Diagnosis Procedure.
- INSPECTION END