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P2A00





2AZ-FXE ENGINE CONTROL: SFI SYSTEM: P2A00: A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)
P2A00 - A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)

DESCRIPTION

HINT
- Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
- Bank 1 sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.
The air fuel ratio sensor generates a voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the hybrid vehicle control ECU with feedback so that it can control the air fuel ratio. The hybrid vehicle control ECU determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection time. If the air fuel ratio sensor malfunctions, the hybrid vehicle control ECU is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the hybrid vehicle control ECU. 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 oxygen concentration 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, therefore the sensor activation is accelerated.

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

*: Value changes inside the hybrid vehicle control ECU. Since the air fuel ratio sensor is a current output element, the current is converted into a voltage inside the hybrid vehicle control ECU. Any measurements taken at the air fuel ratio sensor or hybrid vehicle control ECU connectors will show a constant voltage.









HINT
- When any of these DTCs are set, check the air fuel ratio sensor voltage output by entering the following menus on the Techstream: Powertrain / Engine and ECT / Data List / All Data / AFS Voltage B1S1.
- Short-term fuel trim values can also be read using the Techstream.
- The hybrid vehicle control ECU regulates the voltages at the A1A+ and A1A- terminals of the hybrid vehicle control ECU to a constant level. Therefore, the air fuel ratio sensor voltage output cannot be confirmed without using the Techstream.
- If an air fuel ratio sensor malfunction is detected, the hybrid vehicle control ECU sets a DTC.
MONITOR DESCRIPTION

Sensor Voltage Detection Monitor

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

Example:

If the air fuel ratio sensor voltage output is below 2.8 V (very rich condition) and heated oxygen sensor output voltage falls from 0.59 V or more to less than 0.21 V for 5 seconds, the hybrid vehicle control ECU stores DTC P2196. Alternatively, if the air fuel ratio sensor voltage output is higher than 3.8 V (very lean condition) and heated oxygen sensor output voltage rises from less than 0.21 V to 0.59 V or more for 5 seconds, DTC P2195 is stored.

Sensor Current Detection Monitor

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

If the air fuel ratio sensor output is 3.6 mA or higher for more than 3 seconds of cumulative time, the hybrid vehicle control ECU interprets this as a malfunction in the air fuel ratio sensor and stores DTC P2195 (stuck on high side). If the air fuel ratio sensor output is below 1.0 mA for more than 3 seconds of cumulative time, the hybrid vehicle control ECU stores DTC P2196 (stuck on low side).

- Bank 1 sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.






MONITOR DESCRIPTION

After the engine is warmed up, the hybrid vehicle control ECU performs air fuel ratio feedback control to maintain the air fuel ratio at the stoichiometric level. In addition, active air fuel ratio control is performed for approximately 15 to 25 seconds after preconditions are met in order to measure the air fuel ratio sensor response rate. During active air fuel ratio control, the hybrid vehicle control ECU forcibly increases and decreases the injection volume by a certain amount, based on the stoichiometric air fuel ratio learned during normal air fuel ratio control, and measures the air fuel ratio sensor response rate. The hybrid vehicle control ECU receives a signal from the air fuel ratio sensor while performing active air fuel ratio control and uses it to calculate the air fuel ratio sensor response rate deterioration level.

If the value for the air fuel ratio sensor response rate deterioration level is less than the threshold, the hybrid vehicle control ECU interprets this as a malfunction and stores the DTC.





MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to Checking Monitor Status Mode 6 Data.

CONFIRMATION DRIVING PATTERN

HINT
This confirmation driving pattern is used in the "Perform Confirmation Driving Pattern" procedure of the following diagnostic troubleshooting procedure.

Performing this confirmation pattern will activate the air fuel ratio sensor response monitor.





- Connect the Techstream to the DLC3.

- Turn the power switch on (IG).

- Turn the Techstream on.

- Clear the DTCs DTC Check / Clear.

- Turn the power switch off and wait for at least 30 seconds.

- Turn the power switch on (IG) and turn the Techstream on.

- Enter the following menus: Powertrain / Engine and ECT / Monitor / O2 Sensor.

- Check that the Status2 of O2 Sensor is Incomplete.

- Put the engine in inspection mode Component Tests and General Diagnostics.

- Start the engine and warm it up (until the engine coolant temperature is 75°C (167°F) or higher) [A].

- Drive the vehicle at a constant speed of between 47 and 62 mph (75 and 100 km/h) for 10 minutes [B].

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

- Those items will change to Complete after completing the drive pattern.

- If the values indicated on the Techstream do not change, perform Readiness Monitor Drive Pattern for the air fuel ratio sensor and heated oxygen sensor Monitors, Trips, Drive Cycles and Readiness Codes.

- Check the monitor result values on the Techstream by entering the following menus: Powertrain / Engine and ECT / Monitor / O2 Sensor / Details / RANGE B1S1.

- Note the value of the Monitor Result.

- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

- Read the pending DTC [C].

HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

- Input the DTC: P2A00.

- Check the DTC judgment result.





HINT
If the judgment result shows ABNORMAL, the system has a malfunction.

WIRING DIAGRAM





INSPECTION PROCEDURE

HINT
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the Techstream.

- Connect the Techstream to the DLC3.
- Turn the power switch on (IG) and turn the Techstream on.
- Put the engine in inspection mode Component Tests and General Diagnostics.
- Start the engine.
- Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
- Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
- Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
- Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.
HINT
- The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by -12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.






NOTICE:
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.





- Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.

- To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / All Data / AFS Voltage B1S1 and O2S B1S2; and then press the graph button on the Data List view.

HINT
- DTC P2A00 may be also stored when the air fuel ratio is stuck at rich or lean.
- A low air fuel ratio sensor voltage could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.
- A high air fuel ratio sensor voltage could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.
- Read freeze frame data using the Techstream. The hybrid vehicle control ECU 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.
PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

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

(e) Read the DTCs.

Result:





HINT
If any DTCs other than P2A00 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031

NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - HYBRID VEHICLE CONTROL ECU) P2195

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. PERFORM CONFIRMATION DRIVING PATTERN

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs DTC Check / Clear.

(e) Put the engine in inspection mode Component Tests and General Diagnostics.

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

NEXT -- Continue to next step.

5. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

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

(e) Read the pending DTCs.

Result:





B -- CHECK FOR INTERMITTENT PROBLEMS
A -- Continue to next step.

6. REPLACE AIR FUEL RATIO SENSOR

(a) Replace the air fuel ratio sensor Removal.

NEXT -- Continue to next step.

7. PERFORM CONFIRMATION DRIVING PATTERN

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs DTC Check / Clear.

(e) Put the engine in inspection mode Component Tests and General Diagnostics.

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

NEXT -- Continue to next step.

8. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

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

(e) Read the pending DTCs.

Result:





B -- END

A -- REPLACE HYBRID VEHICLE CONTROL ECU Removal
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