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Home >> Scion >> 2009 >> xB L4-2.4L (2AZ-FE) >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0420

P0420








2AZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0420: Catalyst System Efficiency Below Threshold (Bank 1)

DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

The ECM uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency.
The first sensor, the Air Fuel Ratio (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.
In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air-fuel ratio control.
The OSC value is an indication of the oxygen storage capacity of the TWC. When the vehicle is being driven with a warm engine, active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the ECM deliberately sets the air-fuel ratio to lean or rich levels. If a rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.
The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and sets the DTC.





HINT:
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to CHECKING MONITOR STATUS Mode 6 Data.

CONFIRMATION DRIVING PATTERN
HINT: Performing this confirmation pattern will activate the catalyst monitor. This is very useful for verifying the completion of a repair.




- (a) Connect the Techstream to the DLC3.
- (b) Turn the ignition switch to ON.
- (c) Turn the Techstream ON.
- (d) Clear DTCs (if set) DTC Check / Clear.
- (e) Select the following menu items: Powertrain / Engine and ECT / Monitor.
- (f) Check that Catalyst / Status2 is Incomplete.
- (g) Start the engine and warm it up.
- (h) Drive the vehicle at between 64 km/h and 113 km/h (40 mph and 70 mph) for at least 10 minutes.
- (i) Those items will change to Complete as Catalyst monitor operates.
- (j) Select the following menu items: Powertrain / Engine and ECT / Trouble Codes / Pending.
- (k) Check if any DTCs (any pending DTCs) are set.
HINT: If Catalyst does not change to Complete, and any pending DTCs fail to set, extend the driving time.

CONDITIONING FOR SENSOR TESTING
HINT: Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the Air Fuel Ratio (A/F) sensor and Heated Oxygen (HO2) sensor. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.




- (a) Connect the Techstream to the DLC3.
- (b) Start the engine and warm it up with all the accessories switched OFF until the engine coolant temperature stabilizes.
- (c) Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes.
- (d) While running the engine at 3000 rpm for 2 seconds and 2000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the Techstream.
HINT:
- If either of the voltage outputs of the A/F or HO2 sensor does not fluctuate, or either of the sensors makes a noise, the sensor may be malfunctioning.
- If the voltage outputs of both the sensors remain lean or rich, the air fuel ratio may be extremely lean or rich. In such cases, perform the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
- If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).





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.
3. Turn the Techstream ON.
4. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
5. Select the following menu items: 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) displayed on the Techstream.
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.





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.





- 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: 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: 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.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream ON.
(d) Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.

Result





HINT: If any DTCs other than P0420 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
(a) Connect the Techstream to the DLC3.
(b) Start the engine and warm it up.
(c) Turn the Techstream ON.
(d) Run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(e) Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
(f) Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
(g) Monitor the voltage outputs of the air fuel ratio sensor and heated oxygen sensor (AFS B1S1 and O2S B1S2) displayed on the Techstream.
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:






Result





Lean: During Control the Injection Volume for A/F sensor, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
Rich: During Control the Injection Volume for A/F sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
Lean/Rich: During Control the Injection Volume for A/F sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.

D -- CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO, AND GO TO STEP 3
C -- CHECK FOR EXHAUST GAS LEAK
B -- REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)
A -- Continue to next step.
3. CHECK FOR EXHAUST GAS LEAK
OK:
No gas leak.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.
4. REPLACE EXHAUST MANIFOLD (THREE-WAY CATALYTIC CONVERTER)
(a) Replace the exhaust manifold Removal.
NEXT -- REPLACE CENTER EXHAUST PIPE ASSEMBLY
5. CHECK FOR EXHAUST GAS LEAK
OK:
No gas leak.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- REPLACE HEATED OXYGEN SENSOR (SENSOR 2)
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