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 is a malfunction related to the bank 1 A/F sensor.
- DTC P2A03 is a malfunction related to the bank 2 A/F sensor.
DESCRIPTION
DTC Detecting Condition:
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.
A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydro carbon (HC), and nitrogen oxides (HOx) into less harmful substances. To allow the TWC to function effectively, it is necessary to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio.
*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.
HINT:
- Bank 1 is the bank that includes cylinder No. 1.
- Bank 2 is the bank that includes cylinder No. 2.
- Sensor 1 is the sensor closest to the engine assembly.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions (Part 1):
Typical Enabling Conditions (Part 2):
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 ratio of the A/F sensor when the locus length is short and the response rate has deteriorated.
MONITOR RESULT
Refer to CHECKING MONITOR STATUS. Checking Monitor Status
Wiring Diagram:
Step 1-2:
Step 2(continued):
Step 2(continued)-3:
Step 4-5:
Step 5(continued)-8:
Step 8(continued)-13:
Step 13(continued)-18:
Step 18(continued)-19:
INSPECTION PROCEDURE
HINT:
Intelligent tester only:
The malfunctioning area can be found by the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other suspected areas are malfunctioning or not.
Perform the ACTIVE TEST A/F CONTROL operation.
HINT: The A/F CONTROL operation lowers the injection volume by 12.5 % or increases the injection volume by 25 %.
a. Connect the intelligent tester to the DLC3 on the vehicle.
b. Turn the ignition switch to the ON position.
c. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
d. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
e. Perform the A/F CONTROL operation with the engine idling (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 A/F CONTROL procedure enables the technician to check and graph the voltage outputs of both the A/F sensor and the heated oxygen sensor.
For displaying the graph, enter "ACTIVE TEST / A/F CONTROL / USER DATA", select "AFS B1S1 and O2S B1S2" by pressing "YES" and push "ENTER". Then press "F4".
HINT:
- DTC P2A00 or P2A03 may also be 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 intelligent 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.