P2A00

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

DTC Detection Condition:

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. In addition, the sensor and heater portions are narrower than the conventional 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), 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

Monitor Strategy:

Typical Enabling Conditions (Part 1):

Typical Enabling Conditions (Part 2):

Typical Malfunction Thresholds:

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.

Intelligent tester:
a. Connect an intelligent tester to the DLC3.
b. Turn the engine switch on (IG).
c. Turn the tester ON.
d. Clear DTCs.
e. Enter the following menu: DIAGNOSIS /ENHANCED OBD II / MONITOR INFO / MONITOR RESULT.
f. Check that RES RATE B1S1 and RES RATE B2S1 are INCOMPL.
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 an intelligent tester by selecting the following menu: DIAGNOSIS / ENHANCED OBD II / MONITOR INFO / MONITOR RESULT / RES RATE B1S1 and RES RATE B2S1.
j. If the values indicated on the tester do not change, perform READINESS MONITOR DRIVE PATTERN for the A/F sensor and the heated oxygen sensor.

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. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
m. Check if any DTCs (any pending DTCs) are set.

Techstream:
a. Connect the Techstream to the DLC3.
b. Turn the engine switch on (IG).
c. Turn the tester ON.
d. Clear DTCs (if set).
e. Enter the following menu: Powertrain / Engine / Data List / Monitor Status.
f. Check that O2S(A/FS) Monitor is Incomplete.
g. Start the engine and warm it up.
h. Drive the vehicle at a constant speed of between 25 mph and 75 mph (40 km/h and 120 km/h) for 3 minutes.
i. Check that the status of the O2S(A/FS) Monitor is Complete.
j. Enter the following menu: Powertrain / Engine / Trouble Codes / Pending.
k. Check if any DTCs (any pending DTCs) are set.

MONITOR RESULT

Refer to CHECKING MONITOR STATUS. Mode 6 Data

Wiring Diagram:

Step 1:

Step 1(Continued)-5:

Step 5(Continued)-8:

INSPECTION PROCEDURE

HINT: Malfunctioning areas can be identified by performing the A/F CONTROL*1 (Control the Injection Volume for A/F sensor*2) function provided in the Active Test. The A/F CONTROL (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 A/F CONTROL (Control the Injection Volume for A/ F sensor) operation using the intelligent tester or Techstream.

*1: Intelligent tester
*2: Techstream

1. Connect the intelligent tester or Techstream to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

4. On the tester, enter the following menus:
a. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
b. Techstream - Select: 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 B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.






HINT:
- The A/F CONTROL (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 A/F CONTROL or 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:
1. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2; then press the YES button and the ENTER button followed by the F4 button.
2. Techstream - Select: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 or AFS 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 intelligent tester or 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.