LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2019 >> Yaris LE >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System - Diagnostic Codes (12 Of 13) >> SFI System >> DTC P2251-00: O2 Sensor Negative Current Control Circuit/Open - Bank 1, Sensor 1 [08/2018 - ] >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P2251-00: O2 Sensor Negative Current Control Circuit/Open - Bank 1, Sensor 1 [08/2018 - ]: Procedure

  1. VISUALLY INSPECT ECM CONNECTOR 
    1. Perform the ECM connector Inspection.
    2. Inspect the ECM connector pin type.

      Result

      Result
      200 Pin Type
      186 Pin Type

    Result: 

    186 Pin Type 

    See step  15

    Result: 

    200 Pin Type 

    See step  2

  2. PURPOSE: INSPECT A/F SENSOR CONNECTOR CONDITION 
    1. Switch the ignition off.
    2. Disconnect the A/F sensor connector.
    3. Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
    4. Is there any malfunction?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  14

    Result: 

    No 

    See step  3

  3. PURPOSE: INSPECT ECM CONNECTOR CONDITION 
    1. Disconnect the ECM connector.
    2. Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
    3. Is there any malfunction?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  13

    Result: 

    No 

    See step  4

  4. PURPOSE: INSPECT A/F SENSOR CIRCUIT FOR OPEN CIRCUIT 
    1. Verify that the A/F sensor and ECM connectors are disconnected.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C6-5 - C27-81 Always Below 1 Ω

      Result

      Result
      Yes
      No

    Result: 

    No 

    See step  12

    Result: 

    Yes 

    See step  5

  5. PURPOSE: DETERMINE INTEGRITY OF A/F SENSOR 
    1. Connect the Techstream to the DLC3.
    2. Start the engine and warm it up completely.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1).

      Refer to ON-BOARD DIAGNOSTIC TEST [07/2015 - ]

      Powertrain > Engine > Data List 

      Tester Display
      Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1)
    5. Drive the vehicle under the following conditions.
      WARNING:
      • When the Techstream is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the Techstream using the PID/DATA MONITOR AND RECORD capturing function and inspect later.
      • While performing this step, always operate the vehicle in a safe and lawful manner.
      • After increasing the engine speed to 3000 rpm, decelerate using engine braking.
    6. Is the displayed PID value as follows?
      • Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1): 0.25 mA or more

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  7

    Result: 

    No 

    See step  6

  6. PURPOSE: INSPECT RELATED SENSOR WIRING HARNESS AND CONNECTOR 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1).

      Refer to ON-BOARD DIAGNOSTIC TEST [07/2015 - ]

      Powertrain > Engine > Data List 

      Tester Display
      Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1)
    5. Does the PID value fluctuate when the ECM and A/F sensor connectors are shaken?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  10

    Result: 

    No 

    See step  11

  7. PURPOSE: VERIFICATION OF VEHICLE REPAIR COMPLETION 
    1. Always reconnect all disconnected connectors.
    2. Clear the DTC from the ECM memory using the Techstream.

      Refer to CLEARING DTC [07/2015 - ]

      Powertrain > Engine > Clear DTCs 

    3. Perform the KOER self test.

      Refer to ON-DEMAND SELF-TEST/KEY-ON ENGINE RUNNING SELF-TEST [07/2015 - ]

      Powertrain > Engine > Utility 

      Tester Display
      Key-On Engine Running Self-Test
    4. Is the PENDING CODE for this DTC present?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  9

    Result: 

    No 

    See step  8

  8. PURPOSE: VERIFY IF THERE IS ANY OTHER MALFUNCTION 
    1. Is any other DTC or pending code stored?

      Result

      Result
      Yes
      No

    Result: 

    No 

    DTC TROUBLESHOOTING COMPLETED. 

    Result: 

    Yes 

    GO TO THE APPLICABLE DTC INSPECTION. 

    1. Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2018 - 08/2019] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2019 - ]
  9. REPEAT THE INSPECTION FROM STEP 2. 
    1. If the malfunction recurs, replace the ECM.

      Refer to REMOVAL [07/2015 - ]

    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  8

  10. INSPECT THE RELATED WIRING HARNESS AND CONNECTOR. 
    1. Repair or replace the malfunctioning part.
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  11. REPLACE THE A/F SENSOR. 
    1. Refer to REMOVAL [07/2015 - ]
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  12. REFER TO THE WIRING DIAGRAM AND VERIFY WHETHER OR NOT THERE IS A COMMON CONNECTOR BETWEEN A/F SENSOR TERMINAL C6-5 AND ECM TERMINAL C27-81. 

    If there is a common connector: 

    • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
    • Repair or replace the malfunctioning part.

    If there is no common connector: 

    • Repair or replace the wiring harness which has an open circuit.
    1. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  13. REPLACE THE ECM. 
    1. Refer to REMOVAL [07/2015 - ]
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  14. REPLACE THE A/F SENSOR. 
    1. Refer to REMOVAL [07/2015 - ]
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  15. PURPOSE: INSPECT A/F SENSOR CONNECTOR CONDITION 
    1. Switch the ignition off.
    2. Disconnect the A/F sensor connector.
    3. Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
    4. Is there any malfunction?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  27

    Result: 

    No 

    See step  16

  16. PURPOSE: INSPECT ECM CONNECTOR CONDITION 
    1. Disconnect the ECM connector.
    2. Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
    3. Is there any malfunction?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  26

    Result: 

    No 

    See step  17

  17. PURPOSE: INSPECT A/F SENSOR CIRCUIT FOR OPEN CIRCUIT 
    1. Verify that the A/F sensor and ECM connectors are disconnected.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C35-5 - C28-4 Always Below 1 Ω

      Result

      Result
      Yes
      No

    Result: 

    No 

    See step  25

    Result: 

    Yes 

    See step  18

  18. PURPOSE: DETERMINE INTEGRITY OF A/F SENSOR 
    1. Connect the Techstream to the DLC3.
    2. Start the engine and warm it up completely.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1).

      Refer to ON-BOARD DIAGNOSTIC TEST [07/2015 - ]

      Powertrain > Engine > Data List 

      Tester Display
      Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1)
    5. Drive the vehicle under the following conditions.
      WARNING:
      • When the Techstream is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the Techstream using the PID/DATA MONITOR AND RECORD capturing function and inspect later.
      • While performing this step, always operate the vehicle in a safe and lawful manner.
      • After increasing the engine speed to 3000 rpm, decelerate using engine braking.
    6. Is the displayed PID value as follows?
      • Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1): 0.25 mA or more

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  20

    Result: 

    No 

    See step  19

  19. PURPOSE: INSPECT RELATED SENSOR WIRING HARNESS AND CONNECTOR 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1).

      Refer to ON-BOARD DIAGNOSTIC TEST [07/2015 - ]

      Powertrain > Engine > Data List 

      Tester Display
      Heated Exhaust Gas Oxygen Sensor (bank 1, sensor 1)
    5. Does the PID value fluctuate when the ECM and A/F sensor connectors are shaken?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  23

    Result: 

    No 

    See step  24

  20. PURPOSE: VERIFICATION OF VEHICLE REPAIR COMPLETION 
    1. Always reconnect all disconnected connectors.
    2. Clear the DTC from the ECM memory using the Techstream.

      Refer to CLEARING DTC [07/2015 - ]

      Powertrain > Engine > Clear DTCs 

    3. Perform the KOER self test.

      Refer to ON-DEMAND SELF-TEST/KEY-ON ENGINE RUNNING SELF-TEST [07/2015 - ]

      Powertrain > Engine > Utility 

      Tester Display
      Key-On Engine Running Self-Test
    4. Is the PENDING CODE for this DTC present?

      Result

      Result
      Yes
      No

    Result: 

    Yes 

    See step  22

    Result: 

    No 

    See step  21

  21. PURPOSE: VERIFY IF THERE IS ANY OTHER MALFUNCTION 
    1. Is any other DTC or pending code stored?

      Result

      Result
      Yes
      No

    Result: 

    No 

    DTC TROUBLESHOOTING COMPLETED. 

    Result: 

    Yes 

    GO TO THE APPLICABLE DTC INSPECTION. 

    1. Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2018 - 08/2019] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2019 - ]
  22. REPEAT THE INSPECTION FROM STEP 15. 
    1. If the malfunction recurs, replace the ECM.

      Refer to REMOVAL [07/2015 - ]

    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  21

  23. INSPECT THE RELATED WIRING HARNESS AND CONNECTOR. 
    1. Repair or replace the malfunctioning part.
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

  24. REPLACE THE A/F SENSOR. 
    1. Refer to REMOVAL [07/2015 - ]
    2. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

  25. REFER TO THE WIRING DIAGRAM AND VERIFY WHETHER OR NOT THERE IS A COMMON CONNECTOR BETWEEN A/F SENSOR TERMINAL C35-5 AND ECM TERMINAL C28-4. 

    If there is a common connector: 

    • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
    • Repair or replace the malfunctioning part.

    If there is no common connector: 

    • Repair or replace the wiring harness which has an open circuit.
    1. Go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

  26. REPAIR OR REPLACE THE CONNECTOR AND/OR TERMINALS. 
    1. Then go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

  27. REPAIR OR REPLACE THE CONNECTOR AND/OR TERMINALS. 
    1. Then go to the next step.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

scientia non olet · About LEMON Manuals