SFI SYSTEM, Diagnostic DTC:P0172

DTC Code DTC Name
P0172 System Too Rich Bank 1

DESCRIPTION

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0172 System Too Rich Bank 1

DTC Detection Condition


    Enable Criteria (1)

  • Closed loop fuelling active

  • Mass air flow meter 9.5 g/sec or more, 21 g/sec or less

  • Engine speed 1400 rpm or higher, less than 3100 rpm

  • Engine coolant temperature 80°C (176°F) or higher

  • Intake air temperature -10°C (14°F) or higher

  • Barometric pressure 75.6kpa (570mm Hg) or higher

  • Accumulated mass air flow more than 400gm/sec


    Enable Criteria (2)

  • Closed loop fuelling active

  • Mass air flow meter less than 5 g/sec

  • Engine speed less than 925 rpm

  • Engine coolant temperature 80°C (176°F) or higher

  • Intake air temperature -10°C (14°F) or higher

  • Accumulated mass air flow more than 400 gm/sec


    Malfunction Criteria (1)

  • Long term off idle learn less than -17%


    Malfunction Criteria (2)

  • Long term idle fuel learn less than -300 us


    Diagnostic Mask

  • The MIL will be illuminated if a fault is present for 2 consecutive trips


    Monitor

  • Continuous


    Potential failure modes

  • Fuel Pressure too high

  • Leaking fuel injector

  • Restriction in the exhaust system or air intake / filter

  • Erratic throttle position sensor

  • MAF fault

  • Ignition fault

  • Heated oxygen sensor (sensor1)

  • Intake system

  • Fuel injector assembly

  • Mass air flow meter

  • Engine coolant temperature sensor

  • Ignition system

  • Fuel pressure

  • Gas leak from exhaust system

  • Open or short in heated oxygen sensor (sensor1) circuit

  • Wire harness or connector

  • ECM

  • Heated oxygen sensor (sensor1)

 Comes on DTC stored

MONITOR DESCRIPTION

The oxygen sensor sends a signal to the ECU corresponding to the exhaust gas oxygen content enabling the ECU to maintain a 14.7:1 air/fuel ratio under normal driving conditions. The ECU can make fuel corrections of + 30% to - 30% the calculated fuel demand. This value is then learned by the ECU over time. If the ECU determines a rich condition exists (oxygen sensor above 450 mV), it will decrease the calculated fuel demand to maintain a 14.7:1 ratio. If the ECU determines a lean condition exists (oxygen sensor below 450 mV), it will increase the calculated fuel demand to maintain a 14.7:1 ratio.

WIRING DIAGRAM

Refer to DTC P0102 for the mass air flow meter circuit.

Click here

Refer to DTC P0131 for the oxygen sensor circuit.

Click here

CAUTION / NOTICE / HINT

Note

Inspect the fuses for circuits related to this system before performing the following procedure.

Tech Tips


  • Sensor 1 refers to the sensor closest to the engine assembly.

  • Sensor 2 refers to the sensor farthest away from the engine assembly.

  • Read freeze frame data using the GTS. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

  • A low heated oxygen sensor (sensor 1) voltage could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.

  • A high heated oxygen sensor (sensor 1) voltage could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.

  • If the vehicle is short of fuel, the air fuel ratio becomes lean and the heated oxygen sensor DTCs are recorded, and then the MIL illuminates.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0172)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Trouble Codes.

    5. Read the DTCs.

      Result
      Result Proceed to
      DTC P0172 is output A
      DTC P0172 and other DTCs are output B

      Tech Tips

      If any DTCs other than P0172 are output, troubleshoot those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. READ FREEZE FRAME DATA


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Using the GTS, confirm the vehicle conditions recorded in the freeze frame data which were present when the DTC was stored.

      Click here

    5. Read the value displayed on the GTS.

      Confirmation item
      Engine Speed Fuel System Status Bank1 O2S B1S2
      Calculate Load Short FT B1S1 Evap Purge Flow
      Vehicle Speed Long FT B1S1 MAF
      O2S B1S1 Coolant Temp -
      Result
      Proceed to
      NEXT

    NEXT

  3. PERFORM INITIALIZATION


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

      Result
      Proceed to
      NEXT

    NEXT

  4. READ VALUE USING GTS (SHORT FT B1S1 AND LONG FT B1S1)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Using the GTS, confirm the vehicle conditions recorded in the freeze frame data which were present when the DTC was stored.

    5. Enter the following menus: Powertrain / Engine / Data List / Short FT B1S1 and Long FT B1S1.

    6. Read the value displayed on the GTS.

      Result
      Data List Result Proceed to
      Short FT B1S1 + Long FT B1S1 -16% or higher, or less than 16% A
      Other than above B

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

    B

  5. CHECK FOR EXHAUST GAS LEAK


    1. Check the exhaust gas leaks.

      OK
      No gas leaks.

      Tech Tips

      Perform "Inspection After Repair" after repairing or replacing the exhaust system.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE EXHAUST SYSTEM

    OK

  6. CHECK FUEL PRESSURE


    1. Check the fuel pressure.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    INSPECT FUEL PUMP Click here

    OK

  7. INSPECT FUEL INJECTOR ASSEMBLY


    1. Inspect the fuel injector assembly.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the fuel injector assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FUEL INJECTOR ASSEMBLY Click here

    OK

  8. READ VALUE USING GTS (MAF)


    1. Connect the GTS to the DLC3.

    2. Start the engine.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Data List / Primary / MAF, Coolant Temp and Engine Speed.

    5. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.

    6. Read MAF with the engine speed at 3000 rpm.

      Standard
      GTS Display Condition Specified Condition
      MAF

      Shift lever position: Neutral

      A/C: Off

      Engine Speed: 3000 rpm

      		 Between 5.0 gm/sec and 10.0 gm/sec
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE MASS AIR FLOW METER Click here

    OK

  9. INSPECT ENGINE COOLANT TEMPERATURE SENSOR


    1. Inspect the engine coolant temperature sensor.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

    OK

  10. CHECK EMISSION CONTROL SYSTEM


    1. Check the emission control system.

      Click here

      OK
      No leaks in emission control system.

      Tech Tips


      • Perform "Inspection After Repair" after repairing or replacing the emission control system.

        Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE EMISSION CONTROL SYSTEM

    OK

  11. CHECK INTAKE SYSTEM


    1. Check the intake system for vacuum leaks.

      Click here

      OK
      No leaks in intake system.

      Tech Tips


      • Perform "Inspection After Repair" after repairing or replacing the intake system.

        Click here

      • If a malfunction is detected while the brake pedal is being depressed, vacuum leaks in the brake booster assembly are suspected. Inspect the brake booster assembly.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE INTAKE SYSTEM

    OK

  12. CHECK IGNITION SYSTEM


    1. Check the ignition system.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after repairing or replacing the ignition system.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE INTAKE SYSTEM

    OK

  13. REPLACE HEATED OXYGEN SENSOR (SENSOR 1)


    1. Replace the heated oxygen sensor (sensor 1).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  14. READ VALUE USING GTS (SHORT FT B1S1 AND LONG FT B1S1)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Data List / Short FT B1S1 and Long FT B1S1.

    5. Read the value displayed on the GTS.

      Result
      Data List Result Proceed to
      Short FT B1S1 + Long FT B1S1 -16% or higher, or less than 16% A
      Other than above B

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

    B

  15. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

    Result
    Proceed to
    OK
    NG

    1. Disconnect the A117 mass air flow meter connector.

    2. Disconnect the B142 ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A117-3 (VG) - B142-43 (VG) Always Below 1 Ω
      A117-5 (E2G) - 142-21 (E2G) Always Below 1 Ω
      A117-3 (VG) or B142-43 (VG) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  16. REPLACE MASS AIR FLOW METER


    1. Replace the mass air flow meter.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the mass air flow meter.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  17. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Clear the DTCs.

    5. Turn the engine switch off and wait for at least 30 seconds.

    6. Turn the engine switch on (IG).

    7. Turn the GTS on.

    8. Start the engine and warm it up.

    9. Using the GTS, confirm the vehicle conditions recorded in the freeze frame data which were present when the DTC was stored.

    10. Enter the following menus: Powertrain / Engine / Trouble Codes.

    11. Read the pending DTCs.

      Result
      Result Proceed to
      DTCs are not output A
      DTCP0172 is output B

    A

    END

    B

    REPLACE ECM Click here

  18. INSPECT FUEL PUMP


    1. Inspect the fuel pump.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the fuel pump.

      Click here

      Result
      Proceed to
      OK
      NG

    OK

    REPAIR OR REPLACE FUEL LINE

    NG

    REPLACE FUEL PUMP Click here