P2A00
2UR-FSE 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)
DTC P2A03 - A/F Sensor Circuit Slow Response (Bank 2 Sensor 1)
DESCRIPTION
HINT:
- Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
- 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 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. 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 into a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.
HINT:
- DTCs P2195 and P2196 indicate malfunctions related to bank 1 A/F sensor circuit.
- DTCs P2197 and P2198 indicate malfunctions related to bank 2 A/F sensor circuit.
- Bank 1 refers to the bank that includes No. 1 cylinder.
- Bank 2 refers to the bank that includes No. 2 cylinder.
- When any of these DTCs are set, check the A/F sensor voltage output by entering the following menus:
(1) Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / DATA LIST / A/F CONTROL SYS / AFS B1 S1 or AFS B2 S1.
(2) Techstream - Select: 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 intelligent tester or Techstream.
- The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the A/F sensor voltage output cannot be confirmed without using the intelligent tester or Techstream.
- If a A/F sensor malfunction is detected, the ECM sets a DTC.
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 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 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 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 the threshold, the ECM interprets this as a malfunction and sets the DTC.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data.
WIRING DIAGRAM
CONFIRMATION DRIVING PATTERN
HINT: This confirmation driving pattern is used in the "PERFORM CONFIRMATION DRIVING PATTERN" procedure of the following diagnostic troubleshooting procedure.
NOTE: This test will not be completed if the vehicle is driven under absolutely constant speed conditions such as with cruise control activated.
1 Connect the intelligent tester or Techstream to the DLC3.
2 Turn the power switch ON (READY).
3 Clear DTCs DTC Check / Clear.
4 Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more.
5 Drive the vehicle at between 70 km/h and 120 km/h (45 mph and 75 mph) for at least 10 minutes or more.
6 Stop the vehicle.
7 Turn the tester ON.
8 Enter the following menus:
- Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / MONITOR INFO / ALL READINESS.
- Techstream - Select: Powertrain / Engine and ECT / Utility / All Readiness.
9 Input DTCs: P2A00 and P2A03.
10 Check that DTC MONITOR is PASS DTC not set (NORMAL). If DTC MONITOR is Unavailable (INCOMPLETE), perform the drive pattern by increasing the vehicle speed and using the S2 range to decelerate the vehicle.
INSPECTION PROCEDURE
HINT: Malfunctioning areas can be identified by performing the A/F CONTROL*1 (Control the Injection Volume for A/F sensor*2) function provided in the Active Test. The A/F CONTROL (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 A/F CONTROL (Control the Injection Volume for A/F sensor) operation using the intelligent tester or Techstream.
*1: Intelligent tester
*2: Techstream
1 Connect the intelligent tester or Techstream to the DLC3.
2 Put the engine in inspection mode Inspection Mode Procedure.
3 Turn the tester ON.
4 Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
5 On the tester, enter the following menus:
1 Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
2 Techstream - Select: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
6 Perform the Active Test 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 B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.
HINT:
- The A/F CONTROL (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.
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 A/F CONTROL or 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:
(1) Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2; then press the YES button and the ENTER button followed by the F4 button.
(2) Techstream - Select: 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:
- When viewed from the rear of the engine assembly, Bank 1 is on the left side and Bank 2 is on the right side.
- DTC P2A00 or P2A03 may be also 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 intelligent tester or 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.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00 AND/OR P2A03)
(a) Connect the intelligent tester or Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus:
(1) Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
(2) Techstream - Select: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
Result
HINT: If any DTCs other than P2A00 or P2A03 are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) P0171
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 AND/OR P2A03)
(a) Connect the intelligent tester or Techstream to the DLC3.
(b) Turn the power switch ON (IG) and turn the tester ON.
(c) Enter the following menus:
(1) Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
(2) Techstream - Select: Powertrain / Engine and ECT / Trouble Codes / Pending.
(d) Read DTCs.
Result
B -- CHECK FOR INTERMITTENT PROBLEMS
A -- Continue to next step.
6. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor Removal.
NEXT -- Continue to next step.
7. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.
8. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)
(a) Connect the intelligent tester or Techstream to the DLC3.
(b) Turn the power switch ON (IG) and turn the tester ON.
(c) Enter the following menus:
(1) Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
(2) Techstream - Select: Powertrain / Engine and ECT / Trouble Codes / Pending.
(d) Read DTCs.
Result
B -- CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (REFER TO DTC P0171 PROCEDURE) P0171
A -- END