Mitsubishi Motors Service Manual

2018 / ECLIPSE CROSS / EC - Workshop Manual

13 -FUEL > 13A-DIRECT INJECTION AND MULTIPOINT FUEL INJECTION (DI AND MPI) > TROUBLESHOOTING > DIAGNOSIS CODE PROCEDURES > CODE NO. P0172 ABNORMAL FUEL SYSTEM (RICH)

Code No. P0172: Abnormal Fuel System (rich)

FUNCTION

If the fuel system goes out of order, the fuel correction value will become larger.
The engine-ECU checks whether the fuel trim value is within a specified range.

TROUBLE JUDGEMENT

Check Conditions

Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Fuel injection mode is MPI-mode.

Judgement Criteria

Long-term fuel trim is less than -12.5% for 5 seconds.
Short-term fuel trim is less than -7.8% for 5 seconds.

Long-term fuel trim is less than -12.5% for 2 seconds.
Short-term fuel trim is less than -25.0% for 2 seconds.

Check Conditions

Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Fuel injection mode is not MPI-mode.

Judgement Criteria

Long-term fuel trim is less than -12.5% for 5 seconds.
Short-term fuel trim is less than -7.0% for 5 seconds.

Long-term fuel trim is less than -12.5% for 2 seconds.
Short-term fuel trim is less than -25.0% for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION

None

PROBABLE CAUSES

Failed No. 1 intake air temperature sensor
Failed engine coolant temperature sensor
Failed manifold absolute pressure sensor
Failed air flow sensor
Failed barometric pressure sensor in the engine-ECU
Failed boost pressure sensor
Failed No. 2 intake air temperature sensor
Exhaust leak
Air intake from air flow sensor and all components downstream of it
Failed linear A/F sensor
Failed evaporative emission control system
Failed positive crankcase ventilation valve
Failed injector
Failed injector (high pressure)
Harness damage in fuel system related part(s) circuit or loose connector contact
Contamination around the throttle valve
Incorrect fuel pressure
Use of incorrect or contaminated fuel
Failed engine-ECU

DIAGNOSIS PROCEDURE

Preparation to carry out troubleshooting

Store the freeze frame data of the diagnosis code P0172.

STEP 1. M.U.T.-IIISE diagnosis code

Is any other diagnosis code than P0172 set?

Inspection chart for diagnosis code (Refer to

Go to Step 2.

STEP 2. M.U.T.-IIISE data list

Data list reference table (Refer to ).

Item 5: No. 1 intake air temperature sensor
Item 6: Engine coolant temperature sensor
Item 8: Manifold absolute pressure sensor
Item 10: Air flow sensor
Item BB: Barometric pressure sensor
Item DE: No. 2 intake air temperature sensor
Item 125: Boost pressure sensor 1

Are the check results normal?

YES : Go to Step 3

Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value. Inspection chart for diagnosis code (Refer to

STEP 3. Check crankcase emission control system.

Positive crankcase ventilation system check (Refer to GROUP 17 - Emission Control - Crankcase Emission Control System - Positive Crankcase Ventilation System Check ).
Positive crankcase ventilation valve check (Refer to GROUP 17 - Emission Control - Crankcase Emission Control System - Positive Crankcase Ventilation Valve Check ).

Is the check result normal?

Go to Step 4.

Repair.

STEP 4. Check throttle body (throttle valve portion) contamination.

Is the check result normal?

Go to Step 5.

Throttle body (throttle valve area) cleaning (Refer to

STEP 5. Check air intake from air flow sensor mounting position and all components downstream of it.

Is the check result normal?

Go to Step 6.

Repair.

STEP 6. Check for exhaust leaks

Is the check result normal?

Go to Step 7.

Repair.

STEP 7. Check installation status of linear A/F sensor.

Is the check result normal?

Go to Step 8.

Repair.

STEP 8. M.U.T.-IIISE data list

Data list reference table (Refer to ).

Item E1: Linear A/F sensor

Is the check result normal?

Go to Step 9.

Check linear A/F sensor system. Check code No. P0131: linear A/F sensor circuit low voltage (Refer to

). Check code No. P0132: linear A/F sensor circuit high voltage (Refer to

STEP 9. Check purge control solenoid valve itself.

Purge control solenoid valve check (Refer to GROUP 17 - Emission Control - Evaporative Emission Control System - Purge Control Solenoid Valve Check ).

Is the check result normal?

Go to Step 10.

Replace the purge control solenoid valve.

STEP 10. Check of damage in PURG line between purge control solenoid valve connector and engine-ECU connector.

Is the check result normal?

Go to Step 11.

Repair the connector(s) or wiring harness.

STEP 11. Check of damage in power supply line between engine control relay connector and purge control solenoid valve connector.

Is the check result normal?

Go to Step 12.

Repair the connector(s) or wiring harness.

STEP 12. Check vacuum hose.

Vacuum hose check (Refer to GROUP 17 - Emission Control - Vacuum Hose - Vacuum Hose Check ).

Is the check result normal?

Go to Step 13.

Repair.

STEP 13. Check evaporative emission control system.

Purge control system check (Refer to GROUP 17 - Emission Control - Evaporative Emission Control System - Purge Control System Check ).
Purge port vacuum check (Refer to GROUP 17 - Emission Control - Evaporative Emission Control System - Purge Port Vacuum Check ).

Is the check result normal?

Go to Step 14.

Repair.

STEP 14. Check canister.

Check for leaks from canister or clogged.

Is the check result normal?

Go to Step 15.

Replace the canister.

STEP 15. Check injector itself.

Injector check (Refer to ).

Is the check result normal?

Go to Step 16.

Replace the injector.

STEP 16. Check of damage in INJ1, INJ2, INJ3, INJ4 line between injector connectors and engine-ECU connector.

Are the check results normal?

Go to Step 17.

Repair the connector(s) or wiring harness.

STEP 17. Check of damage in power supply line between engine control relay connector and injector connectors.

Are the check results normal?

Go to Step 18.

Repair the connector(s) or wiring harness.

STEP 18. Check injector (high pressure) itself.

Injector (high pressure) check (Refer to ).

Is the check result normal?

Go to Step 19.

Replace the injector (high pressure).

STEP 19. Check of damage in DI-1, DI-2, DI-3, DI-4 line between injector (high pressure) connectors and engine-ECU connector.

Are the check results normal?

Go to Step 20.

Repair the connector(s) or wiring harness.

STEP 20. Check of damage in DI+1, DI+2, DI+3, DI+4 line between injector (high pressure) connectors and engine-ECU connector.

Are the check results normal?

Go to Step 21.

Repair the connector(s) or wiring harness.

STEP 21. Fuel pressure measurement.

Fuel pressure test (Refer to ).

Is the check result normal?

Go to Step 22.

Repair.

STEP 22. Check fuel.

Check for entry of foreign matter (water, diesel fuel, etc.) into fuel.

Is the check result normal?

Go to Step 23.

Replace the fuel.

STEP 23. After checking stored freeze frame data, check diagnosis codes again.

If diagnosis code P0172 is set while the vehicle is idling, let the vehicle idle for more than 20 minutes.
If diagnosis code P0172 is set while the vehicle is running, let the vehicle run with the same conditions of the freeze frame data, such as the vehicle speed, the crank angle sensor and the coolant temperature sensor, for more than 10 minutes.

Is the diagnosis code P0172 set?

Replace the engine-ECU.

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions