Troubleshooting

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

CIRCUIT DESCRIPTION

DTC Detecting Condition:

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but 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 air-fuel ratio. The A/F sensor has the characteristic that provides output voltage* approximately proportional 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.

By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to perform accurate air-fuel ratio control. The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

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

MONITOR DESCRIPTION

Monitor Description:

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result (Mode 06):

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. A/F sensor response deterioration is determined by the A/F sensor output voltage variation and fuel trim variation.

Wiring Diagram:

Step 1 - 2:

Step 2 (Continued):

Step 2 (Continued) - 6:

Step 7 - 11:

Step 12 - 16:

Step 17:

INSPECTION PROCEDURE

HINT: Read freeze frame data using OBD II scan tool or hand-held tester. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

CONFIRMATION DRIVING PATTERN

Confirmation Driving Pattern:

1. Connect the hand-held tester to the DLC3.
2. Switch the hand-held tester from normal mode to check mode .
3. Start the engine and warm it up for 2 min. or more with all accessory switches OFF.
4. Drive the vehicle at 60 - 120 km/h (38 - 75 mph) and engine speed at 1,600 - 3,200 rpm for 3 - 5 minutes

HINT: If a malfunction exists, the MIL will light up during step (4).

NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will impossible. If you do not have a hand-held tester, turn the ignition switch OFF after performing steps(3) and (4), then perform steps (3) and (4) again.

CHECK FOR INTERMITTENT PROBLEMS

Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect when the ECM is in check mode with hand-held tester. In check mode, the ECM uses 1 trip detection logic, which has a higher sensitivity to malfunctions than normal mode (default), which uses 2 trip detection logic.

a. Clear the DTCs.
b. Set the check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Wiggle the harness and connector.