P2A00
1ZZ-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)
DESCRIPTION
HINT: 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. 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.
HINT:
- When any of these DTCs are set, check the A/F sensor voltage output by selecting the following menu items on Techstream: Powertrain / Engine and ECT / Data List / A/F Control System / AFS B1 S1.
- Short-term fuel trim values can also be read using Techstream.
- The ECM regulates the voltage at the A1A+ and A1A- terminals of the ECM at a constant level. Therefore, the A/F sensor voltage output cannot be confirmed without using Techstream.
- An OBD II scan tool displays the A/F sensor voltage output at a voltage level that is 1/5 of that of the Techstream.
MONITOR DESCRIPTION
The output voltage of the A/F sensor varies in proportion to the air-fuel ratio. Based on these voltage variations, the ECM determines whether the actual air-fuel ratio is rich or lean, and makes adjustments to bring it close to the stoichiometric level. In addition, the ECM checks the fuel injection volume compensation value to determine whether the A/F sensor response time is normal or slow. The ECM calculates the ratio of the variations in both the A/F sensor output voltage and the fuel trim value.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
MONITOR RESULT
The monitor result (mode 6) allows the OBD scan tool to display the monitor status, test value and test limit. A problem in this component can be found by comparing the test value and test limit. This procedure is described in "CHECKING MONITOR STATUS" (Mode 6 Data).
- TID (Test Identification) is assigned to each emission-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
- CID (Component Identification) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD scan tools.
TID $06: A/F Sensor
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT: Techstream only:
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 Techstream.
1. Connect Techstream to the DLC3.
2. Start the engine and turn the tester on.
3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
4. On the tester, select the following menu items: 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:
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, select the following menu items on the tester: 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; then press the graph button on the Data List view.
HINT:
- DTC P2A00 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 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.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00)
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(c) Turn the tester on.
(d) On the tester, select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
Result:
HINT: If any DTCs other than P2A00 are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. READ VALUE OF TECHSTREAM (OUTPUT VOLTAGE OF A/F SENSOR)
(a) Connect Techstream to the DLC3.
(b) Start the engine.
(c) Turn the tester on.
(d) Warm up the Air-Fuel Ratio (A/F) sensor at an engine speed of 2,500 rpm for 90 seconds.
(e) On the tester, select the following menu items: Powertrain / Engine and ECT / Data List / AFS B1 S1 and Engine Speed.
(f) Check the A/F sensor voltage three times, when the engine is in each of the following conditions:
(1) While idling (check for at least 30 seconds) (Step (1)).
(2) At an engine speed of approximately 2,500 rpm (without any sudden changes in engine speed) (Step (2)).
(3) Raise the engine speed to 4,000 rpm and then quickly release the accelerator pedal so that the throttle valve is fully closed (Step (3)).
Standard voltage:
For more information, see the diagrams below.
HINT:
- 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.)
- 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.
- The ECM stops fuel injection (fuel cut) during engine deceleration. This causes a lean condition and results in a momentary increase in the A/F sensor output voltage.
- 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 to learn the closed throttle valve 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; 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 -- INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
OK -- Continue to next step.
3. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.
4. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)
(a) Read DTCs using Techstream.
(b) If using Techstream, select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.
Result:
B -- CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
A -- Continue to next step.
5. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air-fuel ratio sensor.
NEXT -- Continue to next step.
6. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.
7. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)
(a) Read DTCs using Techstream.
(b) If using Techstream, select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.
Result:
NOTE: When replacing the ECM, perform confirmation driving pattern (Monitors, Trips, Drive Cycles and Readiness Codes).
B -- REPLACE ECM
A -- Continue to next step.
8. CONFIRM IF 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 (HEATER RESISTANCE)
(a) Disconnect the A24 A/F sensor connector.
(b) Measure the resistance between the terminals of the A/F sensor connector.
Standard resistance:
(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
10. INSPECT EFI RELAY
(a) Remove the EFI relay from the engine room R/B.
(b) Check the EFI relay resistance.
Standard resistance:
(c) Reinstall the EFI relay.
NG -- REPLACE EFI RELAY
OK -- Continue to next step.
11. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
(a) Disconnect the A24 A/F sensor connector.
(b) Turn the ignition switch to the ON position.
(c) Measure the voltage between the +B terminal of the A/F sensor connector and body ground.
Standard voltage:
(d) Turn the ignition switch 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.
12. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
13. CHECK PCV HOSE (CONNECTIONS)
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
14. CHECK FUEL PRESSURE
(a) Check the fuel pressure (Testing and Inspection).
NG -- REPAIR OR REPLACE FUEL SYSTEM
OK -- Continue to next step.
15. INSPECT FUEL INJECTOR ASSEMBLY
(a) Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) (Testing and Inspection).
NG -- INSPECT FUEL INJECTOR ASSEMBLY
OK -- Continue to next step.
16. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air-fuel ratio sensor.
NEXT -- Continue to next step.
17. PERFORM CONFIRMATION DRIVING PATTERN
NEXT -- Continue to next step.
18. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)
(a) Read DTCs using Techstream.
(b) If using Techstream, select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.
Result:
NOTE: When replacing the ECM, perform confirmation driving pattern (Monitors, Trips, Drive Cycles and Readiness Codes).
B -- REPLACE ECM
A -- Continue to next step.
19. CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
NO -- CHECK FOR INTERMITTENT PROBLEMS
YES -- DTC CAUSED BY RUNNING OUT OF FUEL