Working solution for Lexus IS-F error code P0420

Here is the actual code P0420 information read out from our cars Lexus IS-F, and followed by the error code description, Hint, and solve procedure.

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Error code:
2UR-GSE ENGINE CONTROL: SFI SYSTEM: P0420: Catalyst System Efficiency Below Threshold (Bank 1)

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

DTC P0430 – Catalyst System Efficiency Below Threshold (Bank 2)

DESCRIPTION

The ECM uses sensors mounted in front of and behind the three way catalytic converter to monitor its efficiency.
The first sensor, the air fuel ratio sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.
In order to detect any deterioration in the three way catalytic converter, the ECM calculates the oxygen storage capacity of the three way catalytic converter. This calculation is based on the voltage output of the heated oxygen sensor while performing active air fuel ratio control, rather than the conventional detecting method, which uses the locus ratio.
The oxygen storage capacity value is an indication of the oxygen storage capacity of the three way catalytic converter. 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 heated oxygen sensor is long, the oxygen storage capacity becomes greater. There is a direct correlation between the oxygen storage capacities of the heated oxygen sensor and the three way catalytic converter.
The ECM uses the oxygen storage capacity value to determine the state of the three way catalytic converter. If any deterioration has occurred, it illuminates the MIL and sets a DTC.
HINT:
Bank 1 refers to the bank that includes No. 1 cylinder.
Bank 2 refers to the bank that does not include No. 1 cylinder.
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.

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 engine switch on (IG).
(c) Turn the Techstream ON.
(d) Clear DTCs (if set) See: Reading and Clearing Diagnostic Trouble Codes\DTC Check / Clear.
(e) Enter the following menus: Powertrain / Engine / Monitor.
(f) Check that Catalyst / Status2 is Incomplete.
(g) Start the engine and warm it up.
(h) Drive the vehicle at between 50 mph and 80 mph (80 km/h and 128 km/h) for at least 10 minutes.
(i) Those items will change to Complete as Catalyst monitor operates.
(j) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending; then 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 and heated oxygen sensors. 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 1000 rpm and 2000 rpm for at least 3 minutes.
(d) While running the engine at 2000 rpm for 2 seconds and 1000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the Techstream.
HINT:
If either of the voltage outputs of the air fuel ratio or heated oxygen 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, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
If the three way catalytic converter has deteriorated, the heated oxygen sensor (located behind the three way catalytic converter) 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 sensor, heated oxygen 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.

Connect the Techstream to the DLC3.
Start the engine and turn the Techstream ON.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 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 sensor has an output delay of a few seconds and the heated oxygen 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 air fuel ratio and heated oxygen sensors.
To display the graph, enter the following menus: Powertrain / Engine / 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: Read freeze frame data using the 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

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes.
(d) Read the DTCs.
Result:
HINT: If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

B — GO TO DTC CHART
A — Continue to next step.
PERFORM ACTIVE TEST USING TECHSTREAM (AIR FUEL RATIO CONTROL)(a) Connect the Techstream to the DLC3.
(b) Start the engine and turn the Techstream ON.
(c) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(d) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
(e) 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).
(f)
HINT: Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the Techstream.

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 heated oxygen 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 heated oxygen sensor alternates correctly.

D — INSPECT FOR EXHAUST GAS LEAK
C — INSPECT FOR EXHAUST GAS LEAK
B — CHECK AND REPLACE AIR FUEL RATIO SENSOR
A — Continue to next step.
INSPECT EXHAUST GAS LEAK OK: No gas leaks. NG — REPAIR OR REPLACE EXHAUST GAS LEAK POINT OK — Continue to next step.
CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes.
(d) Read the DTCs.
Result:
B — REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH
A — Continue to next step.
REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY RH(a) Replace exhaust manifold sub-assembly RH See: Engine, Cooling and Exhaust\Exhaust System\Exhaust Manifold\Service and Repair\Removal.
NEXT — REPLACE FRONT EXHAUST PIPE ASSEMBLY

REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH(a) Replace exhaust manifold sub-assembly LH See: Engine, Cooling and Exhaust\Exhaust System\Exhaust Manifold\Service and Repair\Removal.
NEXT — REPLACE FRONT EXHAUST PIPE ASSEMBLY

INSPECT FOR EXHAUST GAS LEAK OK: No gas leaks. NG — REPAIR OR REPLACE EXHAUST GAS LEAK POINT OK — REPLACE HEATED OXYGEN SENSOR
INSPECT FOR EXHAUST GAS LEAK OK: No gas leaks. NG — REPAIR OR REPLACE EXHAUST GAS LEAK POINT OK — CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEARN ACTUAL AIR FUEL RATIO.

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