P2A03

DTC P2A00 A/F SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 1)
DTC P2A03 A/F SENSOR CIRCUIT SLOW RESPONSE (BANK 2 SENSOR 1)

HINT:
- DTC P2A00 means malfunction related to the bank 1 A/F sensor.
- DTC P2A03 means malfunction related to the bank 2 A/F sensor.

CIRCUIT DESCRIPTION

DTC Detecting Condition:

The A/F sensor provides output voltage* approximately equal to the existing air-fuel ratio. The A/F sensor output voltage is used to provide feedback for the ECM to control the air-fuel ratio.

With the A/F sensor output, the ECM can determine deviation from the stoichiometric air-fuel ratio and control proper injection time. If the A/F sensor is malfunctioning, the ECM is unable to accurately control air-fuel ratio.

The A/F sensor is equipped with a heater which heats the zirconia element. The heater is also controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor to facilitate detection of accurate oxygen concentration.

The A/F sensor is a planar type. Compared to a conventional type, the sensor and heater portions are narrower. Because the heat of the heater is conducted through the alumina to zirconia (of the sensor portion), sensor activation is accelerated.

To obtain a high purification rate of the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used. The converter is most efficient when the air-fuel ratio is maintained near the stoichio-metric air-fuel ratio.

*: The voltage value changes on the inside of the ECM only.

HINT:
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that includes cylinder No. 2.
- Sensor 1 refers to the sensor closest to the engine assembly.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

The air-fuel ratio (A/F) sensor varies its output voltage in proportion to the air-fuel ratio. Based on the output voltage, the ECM determines if the air-fuel ratio is RICH or LEAN and adjusts the stoichiometric air-fuel ratio. The ECM also checks the fuel injection volume compensation value to check if the A/F sensor is deteriorating or not. The output voltage variation, known as locus length, should be high when the air-fuel ratio fluctuates. When the A/F sensor response rate has deteriorated, the locus length should be short.

The ECM concludes that there is a malfunction in the A/F sensor when the locus length is short and the response rate has deteriorated.

MONITOR RESULT




Refer to "Checking Monitor Status" for detailed information. Checking Monitor Status

The test value and test limit information are described as shown in the table. Check the monitor result and test values after performing the monitor drive pattern.
- TID (Test Identification Data) is assigned to each emissions-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
- CID (Component Identification Data) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD II scan tools.

Wiring Diagram:

Step 1-2:

Step 2(continued):

Step 3-4:

Step 5:

Step 6-12:

Step 12(continued)-17:

Step 18-19:

INSPECTION PROCEDURE

HINT:
Hand-held tester only:
It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble areas are malfunctioning or not.

a. Perform the ACTIVE TEST A/F CONTROL operation.

HINT: The A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.

1. Connect the hand-held tester to the DLC3 on the vehicle.
2. Turn the ignition switch ON.
3. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
4. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. Perform the A/F CONTROL operation with the engine in an idle condition (press the right or left button).

Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25 % --> RICH output: Less than 3.0 V
-12.5 % --> LEAN output: More than 3.35 V

Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 % --> RICH output: More than 0.55 V
-12.5 % --> LEAN output: Less than 0.4 V

NOTE: The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.




The following procedure of A/F CONTROL enables the user to check its output (show its graph indication) of A/F sensor and heated oxygen sensor.

To display the graph, enter ACTIVE TEST/ A/F CONTROL/USER DATA, then select "AFS B1S1 and O2S B1S2" or "AFS B2S1 and O2S B2S2" by pressing the "YES" button followed by the "ENTER" button and then the "F4" button.

HINT:
- DTC P2A00 or P2A03 may be also detected, 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 with a RICH air-fuel mixture.
- 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 with a LEAN air-fuel mixture.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. The ECM 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 running or stopped, 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.