P2A00

1NZ-FXE 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)

DESCRIPTION

The air-fuel ratio (A/F) sensor provides output voltage* which is almost 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 the 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 carbon monoxides (CO), hydrocarbons (HC) and nitrogen oxides (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 stoichiometric air-fuel ratio.
*: The voltage value changes inside the ECM only.









HINT: Sensor 1 refers to the sensor mounted before the TWC and is located near the engine assembly.

HINT:
- Sensor 1 refers to the sensor closest to the engine assembly.
- The A/F sensor's output voltage and the short-term fuel trim value can be read using Techstream.
- The ECM controls the voltage of the A1A+, and A1A- terminals of the ECM to a fixed voltage. Therefore, it is impossible to confirm the A/F sensor output voltage without Techstream.
- The OBD II scan tool (excluding Techstream) displays the one fifth of the A/F sensor output voltage which is displayed on Techstream.

MONITOR DESCRIPTION





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 STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





COMPONENT OPERATING RANGE





MONITOR RESULT

Refer to detailed information Mode 6 Data.

WIRING DIAGRAM





INSPECTION PROCEDURE
HINT: Malfunctioning areas can be found by performing the Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor operation. The Control the Injection Volume for A/F Sensor operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble area are malfunctioning or not.

(a) Perform the Control the Injection Volume for A/F Sensor operation.
HINT: The Control the Injection Volume for A/F Sensor operation lowers the injection volume 12.5% or increases the injection volume 25%.

(1) Connect Techstream to the DLC3.
(2) Turn the power switch ON (IG).
(3) Put the engine in inspection mode Service Precautions.
(4) Warm up the engine by running the engine at 2,500 rpm, depressing the accelerator pedal more than 60% for approximately 90 seconds.
(5) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
(6) Perform the Control the Injection Volume for A/F Sensor 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 3.1 V
-12.5% = lean output: More than 3.4 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 Control the Injection Volume for A/F Sensor procedure enables the technician to check and graph the voltage output of both A/F sensor and heated oxygen sensor.
To display the graph, enter Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 and O2S B1 S2 then press the graph button on the Data List view.
HINT:
- DTC P2A00 may be also detected, when the air-fuel ratio stays RICH or LEAN.
- Read freeze frame data using Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
- A high A/F sensor voltage could be caused by a RICH air-fuel mixture. Check the conditions that would cause the engine to run with the RICH air-fuel mixture.
- A low A/F sensor voltage could be caused by a LEAN air-fuel mixture. Check the conditions that would cause the engine to run with the LEAN air-fuel mixture.

PROCEDURE

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO A/F SENSOR DTC)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:





HINT: If any other code besides P2A00 are output, perform troubleshooting for those DTCs first.

B -- GO TO DTC CHART
A -- Continue to next step.

2. READ VALUE USING TECHSTREAM (OUTPUT VOLTAGE OF A/F SENSOR)
(a) Connect Techstream to the DLC 3.
(b) Put the engine in inspection mode Service Precautions.
(c) Warm up the A/F sensors (bank 1 sensor 1) by running the engine at 2,500 rpm with the accelerator pedal depressed more than 60% for approximately 90 seconds.
(d) Read A/F sensor voltage output on Techstream.
(e) Enter the following menus: Powertrain / Engine and ECT / Data List.
(f) Select "AFS Voltage B1 S1/Engine Speed" and press button "YES".
(g) Monitor the A/F sensor voltage carefully.
(h) Check the A/F sensor voltage output under the following conditions:
(1) Put the engine in inspection mode and allow the engine to idle for 30 seconds.
(2) Put the engine in inspection mode and running the engine at 2,500 rpm with the accelerator pedal depressed more than 60% (where engine RPM is not suddenly changed).
(3) Deactivate the inspection mode and drive the vehicle with the shift position in "B" range.
(4) Accelerate the vehicle to 44 mph (70 km/h) and quickly release the accelerator pedal so that the throttle valve is fully closed.
CAUTION:
- Strictly observe of posted speed limits, traffic laws, and road conditions when performing these drive patterns.
- Do not drive the vehicle without deactivating inspection mode, otherwise damaging the transaxle may result.

OK:
Condition (1) and (2)
Voltage changes in the vicinity of 3.3 V (between approximately 3.1 to 3.5 V) as shown in the illustration.
Condition (4)
A/F sensor voltage increases to 3.8 V or more during engine deceleration (when fuel cut) as shown in the illustration.




HINT:
- Whenever the output voltage of the A/F sensor remains at approximately 3.3 V (see diagram Malfunction Condition) under any condition as well as the above conditions, the A/F sensor may have an open-circuit. (This will happen also when the A/F sensor heater has an open-circuit.)
- Whenever the output voltage of the A/F sensor remains at a certain value of approximately 3.8 V or more, or 2.8 V or less (see diagram Malfunction Condition) under any condition as well as the above conditions, the A/F sensor may have a short-circuit.
- The ECM will stop fuel injection (fuel cut) during engine deceleration. This will cause a LEAN condition and should result in a momentary increase in A/F sensor voltage output.
- The ECM must establish a closed throttle position learned value to perform fuel cut. If the battery terminal was reconnected, the vehicle must be driven over 10 mph to allow the ECM to learn the closed throttle position.
- When the vehicle is driven:
The output voltage of the A/F sensor may be below 2.8 V during fuel enrichment. For the vehicle, this translates to a sudden increase in speed with the accelerator pedal fully depressed when trying to overtake another vehicle. The A/F sensor is functioning normally.
- The A/F sensor is a current output element, and therefore the current is converted into voltage inside the ECM. If measuring voltage at connectors of A/F sensor or ECM, you will observe a constant voltage.

OK -- PERFORM CONFIRMATION DRIVING PATTERN
NG -- Continue to next step.

3. INSPECT AIR FUEL RATIO SENSOR (RESISTANCE OF A/F SENSOR HEATER)




(a) Disconnect the A5 A/F sensor connector.
(b) Measure the resistance between the terminals of the A/F sensor.
Standard resistance:





(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.

4. INSPECT INTEGRATION RELAY (EFI M RELAY)




(a) Remove the integration relay from the engine room relay block.
(b) Inspect the EFI M relay.
Standard resistance:





(c) Reinstall the integration relay.
NG -- REPLACE INTEGRATION RELAY
OK -- Continue to next step.

5. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)




(a) Disconnect the A5 A/F sensor connector.




(b) Disconnect the E5 ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):





(d) Reconnect the A/F sensor connector.
(e) Reconnect the ECM connector.





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

6. CHECK AIR INDUCTION SYSTEM
(a) Check for vacuum leaks in the air induction system.
OK:
There is no leakage in the air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.

7. CHECK CONNECTION OF PCV HOSE
OK:
PCV hose is connected correctly and PCV hose has no damage.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.

8. CHECK FUEL PRESSURE
OK:
Fuel pressure: 304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44 to 50 psi)
NG -- REPAIR OR REPLACE FUEL SYSTEM
OK -- Continue to next step.

9. INSPECT FUEL INJECTOR ASSEMBLY
(a) Check the injector injection (high or low fuel injection quantity or poor injection pattern).
OK:
Injection volume: 36 to 46 cm3 (2.1 to 2.8 cu in.) per 15 seconds.
NG -- REPLACE FUEL INJECTOR ASSEMBLY
OK -- Continue to next step.

10. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor Removal.
NEXT -- Continue to next step.

11. PERFORM CONFIRMATION DRIVING PATTERN
HINT: Clear all DTCs prior to performing the confirmation driving pattern P2195.

NEXT -- Continue to next step.

12. READ OUTPUT DTC (SEE IF A/F SENSOR DTC IS OUTPUT AGAIN)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:






B -- REPLACE ECM AND PERFORM CONFIRMATION DRIVING PATTERN
A -- Continue to next step.

13. CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
OK:
The vehicle has run out of fuel in the past.
NO -- CHECK FOR INTERMITTENT PROBLEMS
YES -- DTC IS CAUSED BY RUNNING OUT OF FUEL
14. PERFORM CONFIRMATION DRIVING PATTERN
HINT: Clear all DTCs prior to performing the confirmation driving pattern P2195.

GO -- Continue to next step.

15. READ OUTPUT DTC (SEE IF A/F SENSOR DTC IS OUTPUT AGAIN)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:






B -- CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
A -- Continue to next step.

16. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor Removal.
GO -- Continue to next step.

17. PERFORM CONFIRMATION DRIVING PATTERN
HINT: Clear all DTCs prior to performing the confirmation driving pattern P2195.

GO -- Continue to next step.

18. READ OUTPUT DTC (SEE IF A/F SENSOR DTC IS OUTPUT AGAIN)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:






B -- REPLACE ECM AND PERFORM CONFIRMATION DRIVING PATTERN
A -- Continue to next step.

19. CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
OK:
The vehicle has run out of fuel in the past.
NO -- CHECK FOR INTERMITTENT PROBLEMS
YES -- DTC IS CAUSED BY RUNNING OUT OF FUEL