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 the 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 turn ignition switch OFF and wait at least 10 seconds before conducting the next test.

with SDT

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 and select "SELF-LEARNING CONT" in "Utility" mode with SDT.
4) Clear the self-learning control coefficient by touching "CLEAR".
5) 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 [P0172 Fuel Injection System Function] P0172.
If engine does not start, remove ignition plugs and check for fouling, etc.
6) Keep engine at idle for at least 5 minutes.
7) Check 1st trip DTC.
8) The 1st trip DTC P0172 or P0175 should be detected at this stage, if a malfunction exists. If so, go to [P0172 Fuel Injection System Function] P0172.

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 [P0172 Fuel Injection System Function] P0172.

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) Disconnect mass air flow sensor harness connector.





4) Restart engine and let it idle for at least 5 seconds.
5) Stop engine and reconnect mass air flow sensor harness connector.
6) Select Service $03 with GST. Check that DTC P0102 is detected.
7) Select Service $04 with GST and erase the DTC P0102.
8) 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 [P0172 Fuel Injection System Function] P0172
If engine does not start, remove ignition plugs and check for fouling, etc.
9) Keep engine at idle for at least 5 minutes.
10) Check 1st trip DTC.
11) The 1st trip DTC P0172 or P0175 should be detected at this stage, if a malfunction exists. If so, go to [P0172 Fuel Injection System Function] P0172.

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 [P0172 Fuel Injection System Function] P0172.

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.










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










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: VQ40DE] Testing and Inspection.
2 Install fuel pressure gauge and check fuel pressure. Refer to [Fuel Pressure Check: VQ40DE] Testing and Inspection.






OK or NG
OK (With SDT)
GO TO 6.
OK (Without SDT)
GO TO 7.
NG
ERROR! Unknown action!GO TO 5.

5. DETECT MALFUNCTIONING PART

Check the following.
- Fuel pump and circuit (Refer to, [Fuel Pump Circuit Check] Testing and Inspection.)
- Fuel pressure regulator (Refer to [Fuel Pressure Check: VQ40DE] Testing and Inspection.)


Repair or replace.

6. CHECK MASS AIR FLOW SENSOR

With SDT
1 Install all removed parts.
2 Check "MASS AIR FLOW" in "Data list" mode with SDT.






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 MAF Sensor] 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 (P0172)
GO TO 9.
OK (P0175)
GO TO 11.
NG
ERROR! Unknown action!Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to [P0101 MAF Sensor] P0101.

8. CHECK FUNCTION OF FUEL INJECTOR

With SDT
1 Start engine.
2 Perform "POWER BALANCE" in "Active test" mode with SDT.
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 Circuit Check] Testing and Inspection.

9. CHECK FUNCTION OF FUEL INJECTOR-I

Without SDT
1 Stop engine.
2 Disconnect harness connector F44 (3), F201 (1)











3 Turn ignition switch ON.
4 Check voltage between harness connector F44 terminal 3 and ground with SDT or tester.











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.










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 Circuit Check] Testing and Inspection.

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.















OK or NG
OK
GO TO 12.
NG
Perform trouble diagnosis for FUEL INJECTOR, refer to [Fuel Injector Circuit Check] Testing and Inspection.

11. CHECK FUNCTION OF FUEL INJECTOR

1 Start engine.





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






OK or NG
OK
GO TO 12.
NG
Perform trouble diagnosis for FUEL INJECTOR, refer to [Fuel Injector Circuit Check] Testing and Inspection.

12. CHECK FUEL INJECTOR

1 Remove fuel injector assembly. Refer to [Fuel Injector and Fuel Tube: Removal and Installation [VQ40DE] 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. Refer to [Fuel Injector and Fuel Tube: Exploded View [VQ40DE] Exploded View ].

13. CHECK INTERMITTENT INCIDENT

Refer to [Service Information for Electrical Incident: Work Flow] Service Information for Electrical Incident: Work Flow.


INSPECTION END