Toyota Tundra Service Manual: Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1) (P2195-P2198)

DESCRIPTION

The A/F sensor generates a voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio, and regulates the fuel injection time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor in order to facilitate accurate air-fuel ratio detection. In addition, the sensor and heater portions are the narrow type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, and therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the A/F sensor is a current output element, a current is converted into a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.

HINT:

• DTCs P2195 and P2196 indicate malfunctions related to the bank 1 A/F sensor circuit.
• DTCs P2197 and P2198 indicate malfunctions related to the bank 2 A/F sensor circuit.
• When any of these DTCs is stored, check the A/F sensor output voltage by entering the following menus: Powertrain / Engine and ECT / Data List / AFS Voltage B1S1 or AFS Voltage B2S1.
• Short-term fuel trim values can also be read using the Techstream.
• The ECM regulates the voltages at the A1A+ and A1A- or A2A+ and A2A- terminals of the ECM to a constant level. Therefore, the A/F sensor output voltage cannot be confirmed without using the Techstream.
• If the A/F sensor is malfunctioning, the ECM stores DTC P2195, P2196, P2197 or P2198.

MONITOR DESCRIPTION

Under the air-fuel ratio feedback control, if the A/F sensor output voltage indicates rich or lean for a certain period of time, the ECM determines that there is a malfunction in the A/F sensor. The ECM illuminates the MIL and stores a DTC.

Example:

If the A/F sensor output voltage is less than 2.8 V (very rich condition) for 5 seconds, despite the rear HO2 sensor output voltage being less than 0.66 V, the ECM stores DTC P2196 or P2198. Alternatively, if the A/F sensor output voltage is more than 3.8 V (very lean condition) for 5 seconds despite the rear HO2 sensor output voltage being 0.21 V or more, DTC P2195 or P2197 is stored.

A rich air-fuel mixture causes a low A/F sensor current, and a lean air-fuel mixture causes a high A/F sensor current. Therefore, the sensor output becomes low during acceleration, and it becomes high during deceleration with the throttle valve fully closed. The ECM monitors the A/F sensor current during fuel-cut and detects any abnormal current values.

If the A/F sensor output is 2.2 mA or more for more than 3 seconds of cumulative time, the ECM interprets this as a malfunction in the A/F sensor and stores DTC P2195 or P2197 (high-side stuck). If the A/F sensor output is less than 0.7 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 or P2198 (low-side stuck).

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

MONITOR RESULT

Refer to Checking Monitor Status (See page ).

CONFIRMATION DRIVING PATTERN

This confirmation driving pattern is used in the "PERFORM CONFIRMATION DRIVING PATTERN" procedure of the following diagnostic troubleshooting procedure.

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
5. Turn the ignition switch off and wait for at least 30 seconds.
6. Turn the ignition switch to ON and turn the Techstream on.
7. Start the engine, and warm it up until the ECT reaches 75°C (167°F) or higher [A].
8. On the Techstream, enter the following menus to check the fuel-cut status: Powertrain / Engine and ECT / Data List / Idle Fuel Cut.
9. Drive the vehicle at between 60 and 120 km/h (38 and 75 mph) for at least 10 minutes [B].

   CAUTION:

   When performing the confirmation driving pattern, obey all speed limits and traffic laws.

10. Shift the transmission to 2nd gear [C].
11. Accelerate the vehicle to 64 km/h (40 mph) or more by depressing the accelerator pedal for at least 10 seconds [D].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

12. Soon after performing step [D] above, release the accelerator pedal for at least 4 seconds without depressing the brake pedal in order to execute fuel-cut control [E].

    HINT:

    Fuel-cut is performed when the following conditions are met:

    • Accelerator pedal is fully released.
    • Engine speed is 2500 rpm or more (fuel injection returns at 1000 rpm).
13. Allow the vehicle to decelerate until the vehicle speed decreases to less than 10 km/h (6 mph).
14. Repeat steps [C] through [E] above at least 3 times in one driving cycle.
15. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [F].
16. Read the pending DTCs.

    HINT:

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
17. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
18. Input the DTC: P2195, P2196, P2197 or P2198.
19. Check the DTC judgment result.

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    HINT:

    • If the judgment result shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
    • If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [F] again.
20. If no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

• Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. 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 A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
• A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
• Bank 1 refers to the bank that includes the No. 1 cylinder*.

  *: The No. 1 cylinder is the cylinder which is farthest from the transmission.

• Bank 2 refers to the bank that does not include the No. 1 cylinder.
• Sensor 1 refers to the sensor closest to the engine assembly.
• Sensor 2 refers to the sensor farthest away from the engine assembly.

PROCEDURE

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read DTCs.

HINT:

If any DTCs relating to the A/F sensor (DTCs for the A/F sensor heater or A/F sensor admittance) are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

(a) Has the vehicle run out of fuel in the past?

NO

GO TO STEP 4

YES

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON and turn the Techstream on.

(g) Start the engine and warm it up.

(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(i) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

(j) Input the DTC: P2195, P2196, P2197 or P2198.

(k) Check the DTC judgment result.

A

DTC CAUSED BY RUNNING OUT OF FUEL

NG

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear DTCs (See page ).

(e) Drive the vehicle in accordance with the drive pattern described in the CONFIRMATION DRIVING PATTERN.

(f) Enter the following menus: Powertrain / Engine and ECT / Monitor / O2 Sensor.

(g) Check that the status of O2 Sensor is Complete. If the status is still Incomplete, drive the vehicle according to the driving pattern again.

(h) Enter the following menus: Powertrain / Engine and ECT / Monitor / O2 Sensor / Details / RANGE B1S1 or RANGE B2S1.

(i) Check the test value of the A/F sensor output current during fuel-cut.

B

GO TO STEP 16

A

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

(c) Turn the Techstream on.

(d) Warm up the A/F sensor at an engine speed of 2500 rpm for 90 seconds.

(e) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

(f) Monitor the output Voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

HINT:

• Change the fuel injection volume within the range of -12.5% to +12.5%.
• The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
• If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

Standard Voltage:

Lean: During the Control the injection Volume for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.

Rich: During the Control the injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

Lean/Rich: During the Control the injection Volume for A/F Sensor Active Test, the output voltage of the heated oxygen sensor alternates correctly.

B

GO TO STEP 16

A

(a) Check the intake system for vacuum leaks (See page ).

OK:

No leaks in intake system.

HINT:

Perform "Inspection After Repair" after repairing or replacing the intake system (See page ).

NG

REPAIR OR REPLACE INTAKE SYSTEM

OK

(a) Check for exhaust gas leak.

OK:

No gas leak

HINT:

Perform "Inspection After Repair" after repairing or replacing the exhaust system (See page ).

NG

REPAIR OR REPLACE EXHAUST SYSTEM

OK

(a) Check the fuel pressure (See page ).

NG

GO TO STEP 18

OK

(a) Check the fuel injector (whether fuel volume is high or low, and whether injector pattern is poor) (See page ).

HINT:

Perform "Inspection After Repair" after replacing the fuel injector assembly (See page ).

NG

REPLACE FUEL INJECTOR ASSEMBLY

OK

(a) Replace the air fuel ratio sensor (See page ).

HINT:

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (See page ).

NEXT

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off and wait for at least 30 seconds.

(f) Turn the ignition switch to ON and turn the Techstream on.

(g) Start the engine and warm it up.

(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(i) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

(j) Input the DTC: P2195, P2196, P2197 or P2198.

(k) Check the DTC judgment result.

B

END

A

(a) Connect the Techstream to the DLC3.

(b) Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

HINT:

• When performing the Active Test, make sure the shift lever is in P or N.
• The A/C switch and all accessory switches should be off.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.

(e) Confirm the Throttle Idle Position is ON and check the engine idling condition and MAP values in the Data List while performing the Active Test.

HINT:

• Do not leave the EGR valve open for 10 seconds or more during the Active Test.
• Be sure to return the EGR valve to step 0 when the Active Test is completed.

OK:

MAP and idling condition change in response to EGR step position as follows.

Standard:

OK

GO TO STEP 14

NG

(a) Remove the EGR valve assembly (See page ).

(b) Check if the EGR valve is stuck open.

OK:

EGR valve is tightly closed.

HINT:

Perform "Inspection After Repair" after repairing or replacing the EGR valve assembly (See page ).

NG

REPLACE EGR VALVE ASSEMBLY

OK

(a) Replace the ECM (See page ).

NEXT

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTC (See page ).

(e) Turn the ignition switch off and wait for at least 30 seconds.

(f) Turn the ignition switch to ON and turn the Techstream on.

(g) Start the engine and warm it up.

(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(i) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

(j) Input the DTC: P2195, P2196, P2197 or P2198.

(k) Check the DTC judgment result.

NEXT

END

(a) Replace the air fuel ratio sensor (See page ).

HINT:

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (See page ).

NEXT

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off and wait for at least 30 seconds.

(f) Turn the ignition switch to ON and turn the Techstream on.

(g) Start the engine and warm it up.

(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(i) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

(j) Input the DTC: P2195, P2196, P2197 or P2198.

(k) Check the DTC judgment result.

A

END

B

REPLACE ECM

(a) Check the fuel lines for leaks or blockage.

HINT:

Perform "Inspection After Repair" after replacing the fuel pump (See page ).

OK

REPLACE FUEL PUMP

NG

REPAIR OR REPLACE FUEL LINE