P0172

P0172, P0175 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 air fuel ratio (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

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. Start engine again and let it idle for at least 5 minutes.
8. Check 1st trip DTC.
The 1st trip DTC P0172, P0175 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.






CAUTION:
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, remove ignition plugs and check for fouling, etc.

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. Then restart and run engine for at least 5 seconds at idle speed.
6. Stop engine and reconnect mass air flow sensor harness connector.
7. Select Service $03 with GST. Check DTC P0102 is detected.
8. Select Service $04 with GST and erase the DTC P0102.
9. Start engine again and let it idle for at least 5 minutes.
10. Select Service $07 with GST. The 1st trip DTC P0172 or P0175 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.






CAUTION:
Always drive vehicle at a safe speed.
11. If it is difficult to start engine at step 7, the fuel injection system has a malfunction.
12. Crank engine while depressing accelerator pedal.
If engine starts, go to "Diagnosis Procedure". If engine does not start, remove ignition plugs and check for fouling, etc.




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
Listen for an intake air leak after the mass air flow sensor.
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 A/F sensor 1 terminal and ECM terminal as follows. 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 Fuel Pressure Check.
2. Install fuel pressure gauge and check fuel pressure. Refer to Fuel Pressure Check.

At idling: 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 Diagnosis Procedure.)
- Fuel pressure regulator (Refer to Fuel Pressure Check.)
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 P0102.
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 (P0172) - GO TO 9.
OK (P0175) - GO TO 11.
NG - Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to P0102.
8.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.
OK or NG
OK - GO TO 12.
NG - Perform trouble diagnosis for FUEL INJECTOR, refer to Fuel Injector Diagnosis Procedure.
9.CHECK FUNCTION OF FUEL INJECTOR-I
Without CONSULT-III
1. Stop engine.





2. Disconnect harness connector F44 (3), F201 (1)

2 : Vacuum tank
Arrow indicates Front

3. Turn ignition switch ON.





4. Check voltage between harness connector F44 terminal 3 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 and
ECM 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 Fuel Injector Diagnosis Procedure.
10.CHECK FUNCTION OF FUEL INJECTOR-II





Provide battery voltage between harness connector F201 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 Fuel Injector Diagnosis Procedure.
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 Fuel Injector Diagnosis Procedure.
12.CHECK FUEL INJECTOR
1. Remove fuel injector assembly. Refer to 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 about 3 seconds.
Make that sure fuel does not drip from fuel injector.
OK or NG
OK (Does not drip.) - GO TO 13.
NG (Drips.) - Replace the fuel injectors from which fuel is dripping. Always replace O-ring with new one.
13.CHECK INTERMITTENT INCIDENT
Refer to Intermittent Incident.
INSPECTION END