Code No. P0171: Abnormal Fuel System (lean)


OPERATION



  • Check code No. P0201: No. 1 injector system (Refer to ).
  • Check code No. P0202: No. 2 injector system (Refer to ).
  • Check code No. P0203: No. 3 injector system (Refer to ).
  • Check code No. P0204: No. 4 injector system (Refer to ).

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 JUDGMENT


Check Conditions
  • Engine coolant temperature is less than 100°C when the engine is started.
  • Intake air temperature is less than 60°C when the engine is started.
  • Under the closed loop air/fuel ratio control.
  • Engine coolant temperature is more than 79°C.
Judgement Criterion
  • Long-term fuel trim is more than +12.5 % for 5 seconds.


  • Short-term fuel trim is more than +7.0 % for 5 seconds.
Check Conditions
  • Engine coolant temperature is less than 100°C when the engine is started.
  • Intake air temperature is less than 60°C when the engine is started.
  • Under the closed loop air/fuel ratio control.
  • Engine coolant temperature is more than 79°C.
Judgement Criterion
  • Long-term fuel trim is more than +12.5 % for 5 seconds.


  • Short-term fuel trim is more than +12.1 % for 5 seconds.
Check Conditions
  • Engine coolant temperature is more than 100°C when the engine is started.
  • Intake air temperature is more than 60°C when the engine is started.
  • Under the closed loop air/fuel ratio control.
  • Engine coolant temperature is more than 79°C.
Judgement Criterion
  • Long-term fuel trim is more than +12.5 % for 5 seconds.


  • Short-term fuel trim is more than +17.2 % for 5 seconds.
Check Conditions
  • Engine coolant temperature is more than 100°C when the engine is started.
  • Intake air temperature is more than 60°C when the engine is started.
  • Under the closed loop air/fuel ratio control.
  • Engine coolant temperature is more than 79°C.
Judgement Criterion
  • Long-term fuel trim is more than +12.5 % for 5 seconds.


  • Short-term fuel trim is more than +22.3 % for 5 seconds.
Check Conditions
  • Engine coolant temperature is more than 79°C.
  • Under the closed loop air/fuel ratio control.
Judgement Criterion
  • Long-term fuel trim is +12.5 % for 2 seconds.


  • Short-term fuel trim is +25.0 % for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION



  • None

PROBABLE CAUSES



  • Failed intake air temperature sensor
  • Failed engine coolant temperature sensor
  • Failed manifold absolute pressure sensor
  • Air intake from intake hose and intake manifold
  • Air intake around brake booster (such as failed check valve)
  • Exhaust gas leakage from exhaust manifold
  • Failed purge control solenoid valve
  • Harness damage in injector circuit, or connector damage
  • Failed injector
  • Failed fuel supply system (such as failed fuel pressure)
  • Entry of foreign material to fuel (such as water, diesel fuel, water removers and additive)
  • Harness damage in oxygen sensor circuit, or connector damage
  • Failed oxygen sensor (front)
  • Failed installation of oxygen sensor (front)
  • Failed engine-ECU

DIAGNOSIS PROCEDURE
*:Preparation to carry out troubleshooting
    Store the freeze frame data of the diagnosis code P0171.

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

Q. Is any other diagnosis code than P0171 output?
Inspection Chart for Diagnosis Code
Go to Step 2.

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

  • Refer to Data List Reference Table .

  1. Item No. 6: Intake air temperature sensor
  2. Item No. 7: Manifold absolute pressure sensor
  3. Item No. 8: Engine coolant temperature sensor

Q. Are the check results normal?
Go to Step 3.
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 3. Check air intake from intake hose and intake manifold.

Q. Is the check result normal?
Go to Step 4.
Repair.

STEP 4. Check for emission leakage from exhaust manifold.

Q. Is the check result normal?
Go to Step 5.
Repair.

STEP 5. Check installation status of oxygen sensor (front).

Q. Is the check result normal?
Go to Step 6.
Repair.

STEP 6. Connector Check: B-32 oxygen sensor (front) connector

Q. Is the check result normal?
Go to Step 7.
Repair or replace the connector.

STEP 7. Connector Check: B-26 engine-ECU connector

Q. Is the check result normal?
Go to Step 8.
Repair or replace the connector.

STEP 8. Check harness between oxygen sensor (front) connector and engine-ECU connector

  • B-32 (terminal No. 1) oxygen sensor (front) connector and B-26 (terminal No. 38) engine-ECU connector.
  • B-32 (terminal No. 2) oxygen sensor (front) connector and B-26 (terminal No. 39) engine-ECU connector.

  • Check output line and earthing line for damage.

Q. Is the check result normal?
Go to Step 9.
Repair the damaged harness wire.

STEP 9. Check single brake booster check valve.

  • Check valve operation check (Refer to GROUP 35A - Basic Brake System - On-Vehicle Service ).

Q. Is the check result normal?
Go to Step 10.
Replace the check valve.

STEP 10. Check purge control solenoid valve itself.

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

Q. Is the check result normal?
Go to Step 11.
Replace the purge control solenoid valve.

STEP 11. Measure fuel pressure.

  • Measure fuel pressure (Refer to Fuel Pressure Test ).

Q. Is the check result normal?
Go to Step 12.
Repair the fuel pressure.

STEP 12. Connector check: B-101, B-102, B-105, B-106 injector connector

Q. Is the check result normal?
Go to Step 13.
Repair or replace the connector.

STEP 13. Check harness injector connector and engine-ECU connector.

  1. B-101 (terminal No. 2) injector connector and B-26 (terminal No. 2) engine-ECU connector.
  2. B-102 (terminal No. 2) injector connector and B-26 (terminal No. 3) engine-ECU connector.
  3. B-105 (terminal No. 2) injector connector and B-26 (terminal No. 18) engine-ECU connector.
  4. B-106 (terminal No. 2) injector connector and B-26 (terminal No. 19) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 14.
Repair the damaged harness wire.

STEP 14. Connector check: A-70X injector relay connector

Q. Is the check result normal?
Go to Step 15.
Repair or replace the connector.

STEP 15. Check harness injector relay connector and injector connector.

  1. A-70X (terminal No. 3)injector relay connector and B-101 (terminal No. 1) injector connector.
  2. A-70X (terminal No. 3)injector relay connector and B-102 (terminal No. 1) injector connector.
  3. A-70X (terminal No. 3)injector relay connector and B-105 (terminal No. 1) injector connector.
  4. A-70X (terminal No. 3)injector relay connector and B-106 (terminal No. 1) injector connector.
note Before checking harness, check intermediate connector A-17, and repair if necessary.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 16.
Repair the damaged harness wire.

STEP 16. Check injector itself.

  • Check injector itself.

Q. Is the check result normal?
Go to Step 17.
Replace the injector.

STEP 17. Check fuel.

  • Check whether foreign materials enter into fuel such as water, diesel fuel, water removers and additives.

Q. Is the check result normal?
Go to Step 18.
Replace the fuel.

STEP 18. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item No. 11: Oxygen sensor

Q. Is the check result normal?
Go to Step 19.
Replace the oxygen sensor.

STEP 19. After checking stored freeze frame data, check diagnosis codes again.

  • If the diagnosis code P0171 is output while the vehicle is idling, let the vehicle idle for more than 20 minutes.
  • If the diagnosis code P0171 is output 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.

Q. Is the diagnosis code P0171 output?
After replacing the oxygen sensor (front), go to Step 20.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 20. After checking stored freeze frame data, check diagnosis codes again.

  • If the diagnosis code P0171 is output while the vehicle is idling, let the vehicle idle for more than 20 minutes.
  • If the diagnosis code P0171 is output 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.

Q. Is the diagnosis code P0171 output?
Replace the engine-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).
Check end.