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 (TWC), the ECM calculates the Oxygen Storage Capacity (OSC) of the Three-way Catalytic Converter (TWC). This calculation is based on the voltage output of the heated oxygen sensor while performing active air-fuel ratio control.

The OSC value is an indication of the oxygen storage capacity of the Three-way Catalytic Converter (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 the rich-lean cycle of the heated oxygen sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the heated oxygen sensor and Three-way Catalytic Converter (TWC).

The ECM uses the OSC value to determine the state of the Three-way Catalytic Converter (TWC). If any deterioration has occurred, it illuminates the MIL and stores the DTC.

DTC No.	DTC Detection Condition	Trouble Area
P0420	OSC value is less than the standard value under active air-fuel ratio control (2 trip detection logic).	Gas leak from exhaust system Air fuel ratio sensor (for Bank 1 Sensor 1) Heated oxygen sensor (for Bank 1 Sensor 2) Exhaust manifold assembly LH (TWC: Front catalyst) Front No. 2 exhaust pipe assembly (TWC: Rear catalyst)
P0430	OSC value is less than the standard value under active air-fuel ratio control (2 trip detection logic).	Gas leak from exhaust system Air fuel ratio sensor (for Bank 2 Sensor 1) Heated oxygen sensor (for Bank 2 Sensor 2) Exhaust manifold assembly RH (TWC: Front catalyst) Front exhaust pipe assembly (TWC: Rear catalyst)

CATALYST LOCATION

Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1). 1UR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

Text in Illustration
*1	Exhaust Manifold Assembly RH (TWC: Front catalyst)	*2	Exhaust Manifold Assembly LH (TWC: Front catalyst)
*3	Front Exhaust Pipe Assembly (TWC: Rear catalyst)	*4	Front No. 2 Exhaust Pipe Assembly (TWC: Rear catalyst)
*5	Center Exhaust Pipe Assembly	*6	Tailpipe Assembly
*7	Air Fuel Ratio Sensor (for Bank 2 Sensor 1)	*8	Air Fuel Ratio Sensor (for Bank 1 Sensor 1)
*9	Heated Oxygen Sensor (for Bank 2 Sensor 2)	*10	Heated Oxygen Sensor (for Bank 1 Sensor 2)

CONFIRMATION DRIVING PATTERN

HINT:

Performing this confirmation driving pattern will activate the catalyst efficiency monitor. This is very useful for verifying the completion of a repair.

Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1). 1UR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

Connect the GTS to the DLC3.

Turn the engine switch on (IG).

Turn the GTS on.

Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).

Turn the engine switch off and wait for at least 30 seconds.

Turn the engine switch on (IG) and turn the GTS on.

Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher [A].

Drive the vehicle at approximately 60 km/h (37 mph) for 10 minutes or more [B].

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

Drive the vehicle while keeping the engine load as constant as possible.

Turn the engine switch off and wait for at least 30 seconds [C].

Turn the engine switch on (IG) and turn the GTS on.

Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher [D].

Drive the vehicle at approximately 60 km/h (37 mph) for 10 minutes or more [E].

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

Drive the vehicle while keeping the engine load as constant as possible.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [F].

Check if any DTCs (pending DTCs) are set.

HINT:

If the no pending DTCs are stored, perform the following procedure.

Drive the vehicle at a speed between 80 and 100 km/h (50 and 63 mph) for 25 minutes or more [G].

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

Drive the vehicle while keeping the engine load as constant as possible.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [H].

Check if any DTCs (pending DTCs) are stored.

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 to activate the sensors sufficiently to obtain appropriate inspection results.

Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1). 1UR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

(a) Connect the GTS to the DLC3.

(b) Start the engine and warm it up with all the accessories switched off until the engine coolant temperature stabilizes.

(d) While running the engine at 3000 rpm for 2 seconds, and then 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the GTS.

HINT:

If the voltage output of either the air fuel ratio or heated oxygen sensor does not fluctuate, or there is a noise in the waveform of either sensor, 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 Control the Injection Volume for A/F Sensor Active Test using the GTS.

If the Three-way Catalytic Converter (TWC) has deteriorated, the heated oxygen sensor (located behind the Three-way Catalytic Converter (TWC)) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).

Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1). 1UR-FE ENGINE CONTROL. Land Cruiser URJ200 URJ202 GRJ200 VDJ200

INSPECTION PROCEDURE

HINT:

If a malfunction cannot be found when troubleshooting DTC P0420, P0430 a lean or rich abnormality may be the cause. Perform troubleshooting by following the inspection procedure for P0171, P0174 (System Too Lean) and P0172, P0175 (System Too Rich).

After performing repairs, drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern and check if DTC P0420 or P0430 is output again. If a DTC is output again, replace the catalyst if it has not been replaced already.

Read freeze frame data using the GTS. 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.

Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.

Bank 2 refers to the bank that does not include the 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.

1.CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 OR P0430)

Connect the GTS to the DLC3.

Turn the engine switch on (IG).

Turn the GTS on.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result
Result	Proceed to
P0420 or P0430 is output	A
P0420 or P0430 and other DTCs are output	B

HINT:

If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

GO TO DTC CHART ()

A

2.PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)

Connect the GTS to the DLC3.

Start the engine.

Turn the GTS on.

Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.

Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.

Perform the Control the Injection Volume operation with the engine idling.

Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the GTS.

HINT:

Change the fuel injection volume within the range of - 12.5% to +12.5%. The injection volume can be changed in fine gradations.

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.

If the air fuel ratio sensor output voltage does not change (almost no reaction) while performing the Active Test, the air fuel ratio sensor may be malfunctioning.

GTS Display (Sensor)	Injection Volume	Status	Voltage
AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	+12.5%	Rich	Below 3.1 V
AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
O2S B1S2 or O2S B2S2 (Heated oxygen)	+12.5%	Rich	Higher than 0.55 V
O2S B1S2 or O2S B2S2 (Heated oxygen)	-12.5%	Lean	Below 0.4 V

Result:

Status of AFS Voltage B1S1 or AFS Voltage B2S1	Status of O2S B1S2 or O2S B2S2	Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensor Condition	Suspected Trouble Area	Proceed to
Lean/Rich	Lean/Rich	Normal	Three-way catalytic converter Gas leaks from exhaust system	A
Lean	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor	B
Rich	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor	B
Lean/Rich	Lean	Heated oxygen sensor malfunction	Heated oxygen sensor Gas leaks from exhaust system	C
Lean/Rich	Rich	Heated oxygen sensor malfunction	Heated oxygen sensor Gas leaks from exhaust system	C
Lean	Lean	Actual air fuel ratio lean	Extremely rich or lean actual air fuel ratio Gas leaks from exhaust system	D
Rich	Rich	Actual air fuel ratio rich	Extremely rich or lean actual air fuel ratio Gas leaks from exhaust system	D

Lean: During the Control the Injection Volume Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.

Rich: During the Control the Injection Volume Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

Lean/Rich: During the Control the Injection Volume Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternate correctly.

Refer to "Data List / Active Test" [AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2] ().

Go to step 7

Go to step 5

Go to step 6

A

3.CHECK FOR EXHAUST GAS LEAK

Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.

OK:
No gas leaks.

Go to step 8

OK

4.CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)

According to the DTCs output above (Check for Any Other DTCs Output), proceed to the next step referring to the table below.

Result
Result	Proceed to
P0420 is output	A
P0430 is output	B
P0420 and P0430 are output	A and B

REPLACE REPLACE EXHAUST MANIFOLD ASSEMBLY RH AND FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) ()

REPLACE REPLACE EXHAUST MANIFOLD ASSEMBLY LH AND FRONT NO. 2 EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) ()

5.CHECK FOR EXHAUST GAS LEAK

Check for exhaust gas leaks.

OK:
No gas leaks.

Go to step 9

Go to step 8

6.CHECK FOR EXHAUST GAS LEAK

Check for exhaust gas leaks.

OK:
No gas leaks.

Go to step 10

Go to step 8

7.REPLACE AIR FUEL RATIO SENSOR

Replace the air fuel ratio sensor ().

Go to step 11

8.REPAIR OR REPLACE EXHAUST GAS LEAK POINT

Repair or replace exhaust gas leak point.

Go to step 11

9.REPLACE HEATED OXYGEN SENSOR

Replace the heated oxygen sensor ().

Go to step 11

10.CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 Inspection Procedure ()

NEXT

11.CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

Connect the GTS to the DLC3.

Turn the engine switch on (IG).

Turn the GTS on.

Clear the DTCs ().

Turn the engine switch off and wait at least 30 seconds.

Turn the engine switch on (IG) and turn the GTS on.

Start the engine.

Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result
Result	Proceed to
DTC P0420 and/or P0430 is output	A
DTC is not output	B

END

A

12.CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)

Connect the GTS to the DLC3.

Turn the engine switch on (IG).

Turn the GTS on.

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result
Result	Proceed to
DTC P0420 is output	A
DTC P0430 is output	B
DTC P0420 and P0430 are output	A and B

REPLACE REPLACE EXHAUST MANIFOLD ASSEMBLY RH AND FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) ()

REPLACE REPLACE EXHAUST MANIFOLD ASSEMBLY LH AND FRONT NO. 2 EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) ()

1UR-FE ENGINE CONTROL

Land Cruiser URJ200 URJ202 GRJ200 VDJ200

SFI SYSTEM