RX400h · Service Manual ENGINE

P2A00 Air-Fuel Ratio (A/F) sensor circuit slow response:Under condition (a), (b) and (c), A/F sensor output voltage...

Diagnostic trouble codes

DESCRIPTION

  1. DTC P2A00 indicates malfunctions related to the bank 1 A/F sensor.
  2. DTC P2A03 indicates malfunctions related to the bank 2 A/F sensor.
  3. Bank 1 refers to the bank that includes cylinder No. 1.
  4. Bank 2 refers to the bank that includes cylinder No. 2.
  5. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
The A/F sensor generates voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM (Included in HV Control ECU) 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 though 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.
A107164E03
DTC No.
 DTC Detection Condition
 Trouble Area
P2A00
P2A03
  1. Air-Fuel Ratio (A/F) sensor circuit slow response:
    Under condition (a), (b) and (c), A/F sensor output voltage changing value below regular changing value in comparison with fuel trim changing value (2 trip detection logic):
    1. Warm engine
    2. Driving at engine speed of between 950 rpm and 2,500 rpm
    3. Vehicle speed between 37.5 mph and 75 mph (60 km/h and 120 km/h)
  1. Open or short in A/F sensor (bank 1, 2 sensor 1)
  2. A/F sensor (bank 1, 2 sensor1)
  3. A/F sensor heater
  4. A/F HTR relay
  5. Open or short in A/F sensor heater and relay circuits
  6. Air induction system
  7. Fuel pressure
  8. Injector
  9. PCV valve and hose
  10. PCV hose connection
  11. HV Control ECU

WIRING DIAGRAM

Refer to DTC P2195 (Click here).

INSPECTION PROCEDURE

HINT:
Intelligent tester only:
Malfunctioning areas can be identified by performing the A/F Control function provided in the Active Test. The A/F Control 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 A/F Control operation using the intelligent tester.
  1. Connect the intelligent tester to the DLC3.
  2. Put the engine in inspection mode (Click here).
  3. Start the engine and turn the tester ON.
  4. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
  5. On the intelligent tester, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
  6. Perform the A/F Control operation with the engine in an idling condition (press the Right or Left button to change the fuel injection volume).
  7. Monitor the output voltages of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

HINT:
  1. The A/F Control operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
  1. Each sensor reacts in accordance with increases in the fuel injection volume.


Standard:
Tester Display
(Sensor)
 Injection Volume
 Status
 Voltage
AFS B1S1 or AFS B2S1
(A/F)
 +25 %
 Rich
 Less than 3.0
AFS B1S1 or AFS B2S1
(A/F)
 -12.5 %
 Lean
 More than 3.35
O2S B1S2 or O2S B2S2
(HO2)
 +25 %
 Rich
 More than 0.55
O2S B1S2 or O2S B2S2
(HO2)
 -12.5 %
 Lean
 Less than 0.4

NOTICE:
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.

Case
 A/F Sensor (Sensor 1)
Output Voltage
 HO2 Sensor (Sensor 2)
Output Voltage
 Main Suspected Trouble Area
1
 Injection Volume
+25 %
-12.5 %
 A103184
 Injection Volume
+25 %
-12.5 %
 A103184
 -
Output Voltage
More than 3.35 V
Less than 3.0 V
 A107708
 Output Voltage
More than 0.55 V
Less than 0.4 V
 A103186
2
 Injection Volume
+25 %
-12.5 %
 A103184
 Injection Volume
+25 %
-12.5 %
 A103184
  1. A/F sensor
  2. A/F sensor heater
    A/F sensor circuit
Output Voltage
Almost
no reaction
 A103185
 Output Voltage
More than 0.55 V
Less than 0.4 V
 A103186
3
 Injection Volume
+25 %
-12.5 %
 A103184
 Injection Volume
+25 %
-12.5 %
 A103184
  1. HO2 sensor
  2. HO2 sensor heater
  3. HO2 sensor circuit
Output Voltage
More than 3.35 V
Less than 3.0 V
 A107708
 Output Voltage
Almost
no reaction
 A103185
4
 Injection volume
+25 %
-12.5 %
 A103184
 Injection Volume
+25 %
-12.5 %
 A103184
  1. Injector
  2. Fuel pressure
  3. Gas leakage from exhaust system
    (Air-fuel ratio extremely lean or rich)
Output Voltage
Almost
no reaction
 A103185
 Output Voltage
Almost
no reaction
 A103185
Following the A/F Control procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

HINT:
  1. DTC P2A00 or P2A03 may be also set, when the air-fuel ratio is stuck rich or lean.
  2. 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.
  3. 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.
  4. Read freeze frame data using the intelligent tester. 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.


1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00 AND/OR P2A03)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch ON.

  1. Turn the tester ON.

  1. Enter the following menus: Powertrain / Engine / DTC.

  1. Read DTCs.

    Result:
    Display (DTC Output)
    		 Proceed to
    P2A00 and/or P2A03
    		 A
    P2A00 and/or P2A03 and other DTCs
    		 B

    HINT:
    If any DTCs other than P2A00 or P2A03 are output, troubleshoot those DTCs first.



 B
GO TO DTC CHART
A


2. READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF A/F SENSOR)

  1. Connect the intelligent tester to the DLC3.

  1. Put the engine in inspection mode (Click here).

  1. Start the engine.

  1. Turn the tester ON.

  1. Warm up the Air-Fuel Ratio (A/F) sensor at an engine speed of 2,500 rpm for 90 seconds.

  1. On the tester, enter the following menus: Powertrain / Engine / Data List / Custom List/ AFS B1S1 or AFS B2S1 and Engine Speed / Record.

  1. Check the the A/F sensor voltage three times, when the enigne is in each of the following conditions:

    1. While idling (check for at least 30 seconds)

    2. At an engine speed of approximately 2,500 rpm (without any sudden changes in engine speed)

    3. Raise the engine speed to 4,000 rpm and then quickly release the accelerator pedal so that the throttle valve is fully closed.

      Standard voltage:
      Condition
      		 A/F Sensor Voltage Variation
      		 Reference
      (1) and (2)
      		 Changes at approximately 3.3 V
      		 Between 3.1 V and 3.5 V
      (3)
      		 Increases to 3.8 V or more
      		 This occurs during engine deceleration
      when fuel-cut performed

      HINT:
      For more information, see the diagrams below.

      A107161E01

      HINT:
      1. If the output voltage of the A/F sensor remains at approximately 3.3 V (see Malfunction Condition diagram) under any conditions, including those above, the A/F sensor may have an open circuit. (this will also happen if the A/F sensor heater has an open circuit.)
      2. If the output voltage of the A/F sensor remains at either approximately 3.8 V or more, or 2.8 V or less (see Malfunction Condition diagram) under any conditions, including those above, the A/F sensor may have a short circuit.
      3. The ECM (Included in HV Control ECU) stops fuel injection (fuel cut) during engine deceleration. This causes a lean condition and result in a momentary increase in the A/F sensor output voltage.
      4. The ECM must establish a closed throttle valve position learning value to perform fuel cut. If the battery terminal has been reconnected, the vehicle must be driven over 10 mph (16 km/h) to allow the ECM terminal has been reconnected, the vehicle must be driven over 10 mph (16 km/h) to allow the ECM to learn the closed throttle valve position.
      5. 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.
      6. The A/F sensor is a current output element; therefore, the current is converted into a voltage inside the ECM. Measuring the voltage at the connectors of the A/F sensor or ECM will show a constant voltage result.



 NG
Go to step 9
OK


3. PERFORM CONFIRMATION DRIVING PATTERN

NEXT


4. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

  1. Read DTCs using the intelligent tester.

  1. Enter the following menus: Powertrain / Engine / DTC / Pending.

    Result:
    Display (DTC Output)
    		 Proceed to
    P2A00 and/or P2A03
    		 A
    No output
    		 B



B
Go to step 8
A


5. REPLACE AIR FUEL RATIO SENSOR

NEXT


6. PERFORM CONFIRMATION DRIVING PATTERN

NEXT


7. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

  1. Read DTCs using the intelligent tester.

  1. Enter the following menus: Powertrain / Engine / DTC / Pending.

    Result:
    Display (DTC Output)
    		 Proceed to
    No output
    		 A
    P2A00 and/or P2A03
    		 B



B
REPLACE HV CONTROL ECU AND PERFORM CONFIRMATION DRIVING PATTERN
A


8. CONFIRM WHETHER VEHICLE HAS RUN OUT OF FUEL IN PAST


NO
CHECK FOR INTERMITTENT PROBLEMS
YES

DTC CAUSED BY RUNNING OUT OF FUEL

9. INSPECT AIR FUEL RATIO SENSOR

  1. A052607E13
    Disconnect the A3 or A4 A/F sensor connector.

  1. Measure the resistance between the terminals of the A/F sensor connector.

    Standard resistance:
    Tester Connection
    		 Specified Condition
    HA1A, HA2A (1) - +B (2)
    		 1.8 Ω to 3.4 Ω at 20°C (68°F)
    HA1A, HA2A (1) - A1A-, A2A- (4)
    		 10 kΩ or higher

  1. Reconnect the A/F sensor connector.



 NG
REPLACE AIR FUEL RATIO SENSOR
OK


10. INSPECT A/F RELAY

  1. B016200E02
    Remove the A/F relay from the engine room R/B.

  1. Measure A/F relay resistance.

    Standard resistance:
    Tester Connection
    		 Specified Condition
    3 - 5
    		 10 kΩ or higher
    3 - 5
    		 Below 1 Ω
    (when battery voltage applied to terminals 1 and 2)

  1. Reinstall the A/F relay.



 NG
REPLACE A/F RELAY
OK


11. CHECK HARNESS AND CONNECTOR (A/F SENSOR -HV CONTROL ECU)

  1. A110913E03
    Disconnect the A3 and A4 A/F sensor connector.

  1. Turn the ignition switch ON.

  1. Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

    Standard voltage:
    Tester Connection
    		 Specified Condition
    +B (2) - Body ground
    		 9 to 14 V

  1. Turn the ignition switch off.

  1. Disconnect the H33 HV Control ECU connector.

  1. Measure the resistance between the terminals of the A/F sensor and HV Control ECU.

    Standard resistance (Check for open):
    Tester Connection
    		 Specified Condition
    HA1A ( A4-1) - HA1A (H33-4)
    		 Below 1 Ω
    A1A+ (A4-3) - A1A+ (H33-22)
    		 Below 1 Ω
    A1A- (A4-4) - A1A- (H33-30)
    		 Below 1 Ω
    HA2A (A3-1) - HA2A (H33-3)
    		 Below 1 Ω
    A2A+ (A3-3) - A2A+ (H33-23)
    		 Below 1 Ω
    A2A- (A3-4) - A2A- (H33-31)
    		 Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		 Specified Condition
    HA1A( A4-1) or HA1A (H33-4) - Body ground
    		 10 kΩ or higher
    A1A+ (A4-3) or A1A+ (H33-22) - Body ground
    		 10 kΩ or higher
    A1A- (A4-4) or A1A- (H33-30) - Body ground
    		 10 kΩ or higher
    HA2A (A3-1) or HA2A (H33-3) - Body ground
    		 10 kΩ or higher
    A2A+ (A3-3) or A2A+ (H33-23) - Body ground
    		 10 kΩ or higher
    A2A- (A3-4) or A2A- (H33-31) - Body ground
    		 10 kΩ or higher

  1. Reconnect the HV Control ECU connector.

  1. Reconnect the A/F sensor connector.



 NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


12. CHECK AIR INDUCTION SYSTEM

  1. Check the air induction system for vacuum leakage.

    OK:
    No leakage from air induction system.



 NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK


13. CHECK PCV HOSE

OK:
PCV hose is connected correctly and is not damaged.



 NG
REPAIR OR REPLACE PCV HOSE
OK


14. CHECK FUEL PRESSURE

  1. Check the fuel pressure (Click here).

    Standard:
    304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44.1 to 49.7 psi)



 NG
REPAIR OR REPLACE FUEL SYSTEM
OK


15. INSPECT FUEL INJECTOR

  1. Check the injector injection (Click here).

    Standard:
    13 cm3 (0.8 cu in.) or less



 NG
REPLACE FUEL INJECTOR ASSEMBLY
OK


16. REPLACE AIR FUEL RATIO SENSOR

NEXT


17. PERFORM CONFIRMATION DRIVING PATTERN

NEXT


18. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

  1. Read DTCs using the intelligent tester.

  1. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.

    Result:
    Display (DTC Output)
    		 Proceed to
    No output
    		 A
    P2A00 and/or P2A03
    		 B



B
REPLACE HV CONTROL ECU
A


19. CONFIRM WHETHER VEHICLE HAS RUN OUT OF FUEL IN PAST


NO
CHECK FOR INTERMITTENT PROBLEMS
YES

DTC CAUSED BY RUNNING OUT OF FUEL


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