P2A00

2TR-FE 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)

CAUTION / NOTICE / HINT

HINT: Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

DESCRIPTION

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), current flows into the heater to heat the sensor, in order to facilitate accurate air-fuel ratio 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 to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.









HINT:
- When any of these DTCs are set, check the A/F sensor voltage output by entering the following menus: Powertrain / Engine and ECT / Data List / A/F Control System / AFS B1 S1 or AFS B2 S1.
- Short-term fuel trim values can also be read using the Techstream.
- The ECM regulates the voltages at the A1A+ and A1A- terminals of the ECM to a constant level. Therefore, the A/F sensor voltage output cannot be confirmed without using the Techstream.
- If the A/F sensor is malfunctioning, the ECM sets the DTC P2A00.

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 ratio 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 ratio 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 ratio 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 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 ignition switch to ON.

(c) Turn the tester ON.

(d) Clear DTCs (if set).

(e) Select the following menu items: Powertrain / Engine and ECT / Monitor / O2 Sensor / Details.

(f) Check that RES RATE B1S1 is 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 test result values on the Techstream by selecting the following menu items: Powertrain / Engine and ECT / Monitor / O2 Sensor.

(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 (Monitors, Trips, Drive Cycles and Readiness Codes).

HINT: Completion of all A/F sensor monitors is required to change the value in Test Result.

(k) Note the value of the Monitor Result.

(l) Select the following menu items: 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






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 tester ON.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
6. Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and OS2 B1S2) displayed on the tester.

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.
Standard Voltage:






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 and ECT / 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 may be 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.
- DTC P2A00 may also be set, when the sensor element is electrically clogged or contaminated.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
Result:





If any DTCs relating to the A/F sensor (DTCs for the A/F sensor heater or A/F sensor admittance) are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)





(a) Disconnect the A4 Air-Fuel Ratio (A/F) sensor connector.
(b) Measure the resistance between the terminals of the A/F sensor connector.
Standard Resistance:





(c) Reconnect the air-fuel ratio sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (ECM - AIR FUEL RATIO SENSOR)





(a) Disconnect the A4 A/F sensor connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage between the +B terminal of the A/F sensor connector and body ground.
Standard Voltage:





(d) Turn the ignition switch to OFF.
(e) Disconnect the E4 ECM connector.
(f) Check the resistance.
Standard Resistance (Check for open):





Standard Resistance (Check for short):





(g) Reconnect the ECM connector.
(h) Reconnect the A/F sensor connector.





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)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
(d) Read pending DTCs.
Result:





B -- CHECK FOR INTERMITTENT PROBLEMS
A -- Continue to next step.
6. REPLACE AIR FUEL RATIO SENSOR
NEXT -- Continue to next step.
7. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.
8. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON and turn the tester ON.
(c) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
(d) Read pending DTCs.
Result:





B -- CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (REFER TO DTC P0171 PROCEDURE)
A -- END