P2A03

1UR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2A00: A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)

DTC P2A00 - A/F Sensor Circuit Slow Response (Bank 1 Sensor 1)

DTC P2A03 - A/F Sensor Circuit Slow Response (Bank 2 Sensor 1)

DESCRIPTION

HINT:
- Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

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 level, 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 oxygen concentration detection. 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), 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 the 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:
- DTC P2A00 indicates malfunctions related to the bank 1 A/F sensor.
- DTC P2A03 indicates malfunctions related to the bank 2 A/F sensor.
- Bank 1 refers to the bank that includes No. 1 cylinder.
- Bank 2 refers to the bank that includes No. 2 cylinder.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.





MONITOR DESCRIPTION

After engine is warmed up, the ECM performs air-fuel ratio feedback control to maintain the air-fuel ratio at the stoichiometric level. In addition, active A/F control is performed for approximately 10 seconds after preconditions are met in order to measure the A/F sensor response rate. During active A/F control, the ECM forcibly increases and decreases the injection volume a certain amount, based on the stoichiometric air-fuel ratio learned during normal air-fuel ratio control, and measures the A/F sensor response rate. The ECM receives a signal from the A/F sensor while performing active A/F control and uses it to calculate the A/F sensor response rate deterioration level.
If the value for A/F sensor response rate deterioration level is less than the threshold, the ECM interprets this as a malfunction and sets the DTC.





CONFIRMATION DRIVING PATTERN
HINT: Performing this confirmation pattern will activate the A/F sensor response monitor.




- (a) Connect the Techstream to the DLC3.
- (b) Turn the engine switch on (IG).
- (c) Turn the Techstream ON.
- (d) Clear DTCs DTC Check / Clear.
- (e) Enter the following menu: Powertrain / Engine and ECT / Monitor / O2 Sensor / Details.
- (f) Check that RES RATE B1S1 and RES RATE B2S1 are Incomplete.
- (g) Start the engine and warm it up.
- (h) Drive the vehicle at between 25 mph and 75 mph (40 km/h and 120 km/h) for 3 minutes. However, the vehicle should be driven at a constant speed.
- (i) Check the monitor result values on the Techstream by entering the following menus: Powertrain / Engine and ECT / Monitor / O2 Sensor / Details / RES RATE B1S1 or RES RATE B2S1 / Details.
- (j) If the values indicated on the Techstream do not change, perform READINESS MONITOR DRIVE PATTERN for the A/F sensor and the heated oxygen sensor Monitors, Trips, Drive Cycles and Readiness Codes.
HINT: Completion of all A/F sensor monitors is required to change the value in RES RATE B1S1 and RES RATE B2S1.
- (k) Note the value of the RES RATE B1S1 and RES RATE B2S1.
- (l) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
- (m) Check if any DTCs (any pending DTCs) are set.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to CHECKING MONITOR STATUS Mode 6 Data.

WIRING DIAGRAM





CONFIRMATION DRIVING PATTERN

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








- (a) Connect the Techstream to the DLC3.
- (b) Turn the engine switch on (IG).
- (c) Turn the Techstream ON.
- (d) Clear DTCs DTC Check / Clear.
- (e) Start the engine, and warm it up until the ECT reaches 75°C (167°F) or higher.
- (f) Enter the following menus to check the fuel-cut status: Powertrain / Engine / Data List / All Data / Idle Fuel Cut.
- (g) Drive the vehicle at between 38 mph (60 km/h) and 75 mph (120 km/h) for at least 10 minutes.
- (h) Change the transmission to 2nd gear.
- (i) Drive the vehicle at proper vehicle speed to perform fuel-cut operation (refer to the following HINT).
HINT: Fuel-cut is performed when the following conditions are met:
- Accelerator pedal fully released.
- Engine speed is 2500 rpm or more (fuel injection returns at 1000 rpm).
- (j) Accelerate the vehicle to 40 mph (64 km/h) or more by depressing the accelerator pedal for at least 10 seconds.
- (k) Soon after performing step (j) above, release the accelerator pedal for at least 4 seconds without depressing the brake pedal, in order to execute fuel-cut control.
- (l) Allow the vehicle to decelerate until the vehicle speed declines to less than 6 mph (10 km/h).
- (m) Repeat steps from (h) through (k) above at least 3 times in one driving cycle.
HINT: Completion of all O2S (A/F) Monitor is required to change the value in Data List.
CAUTION:
Strictly observe posted speed limits, traffic laws, and road conditions when performing these drive patterns.

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 (A/F) sensor, Heated Oxygen (HO2) 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.

1 Connect the Techstream to the DLC3.
2 Start the engine and turn the Techstream ON.
3 Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4 Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
5 Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
6 Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1 S1 and O2S B1 S2 or AFS Voltage B2 S1 and O2S B2 S2) 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.





NOTE:
The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) 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 A/F and HO2 sensors.
- To display the graph, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 and O2S B1 S2 or AFS Voltage B2 S1 and O2S B2 S2.
HINT:
- DTC P2A00 or P2A03 may be also set, when the air-fuel ratio is stuck rich or lean.
- 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.
- 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.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00 AND/OR P2A03)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream ON.
(d) Enter the following menus: Powertrain / Engine / Trouble Codes.
(e) Read DTCs.
Result:





HINT: If any DTCs other than P2A00 or P2A03 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
C -- REPLACE AIR FUEL RATIO SENSOR
B -- REPLACE AIR FUEL RATIO SENSOR
A -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) P0171
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.

5. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
(d) Read 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.
HINT:
- for 2WD Removal.
- for AWD Removal.

NEXT -- Continue to next step.

7. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.

8. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
(d) Read DTCs.
Result:






B -- CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

1. CHECK ANY OTHER DTCS OUTPUT
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes.
(d) Read the DTCs.
Result:





HINT: If any DTCs other than P0171, P0172, P0174, P0175, P1170 or P117B are output, troubleshoot those DTCs first.


A -- END