2Tr-Fe Engine Control. Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1)

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 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) Front exhaust pipe assembly (TWC: Front catalyst and rear catalyst)

CATALYST LOCATION

Hilux. Tgn26, 36 Kun25, 26, 35, 36 Ggn25.2Tr-Fe Engine Control.Sfi System (W/ Secondary Air Injection System).
Dtc
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

Text in Illustration
*1	Exhaust Manifold	*2	Air Fuel Ratio Sensor
*3	TWC: Front Catalyst	*4	TWC: Rear Catalyst
*5	Front Exhaust Pipe Assembly	*6	Heated Oxygen Sensor
*7	Center Exhaust Pipe Assembly	*8	Tailpipe Assembly

MONITOR STRATEGY

Required Sensors/Components (Main)	Air fuel ratio sensor, heated oxygen sensor
Required Sensors/Components (Related)	Intake air temperature sensor, mass air flow meter, crankshaft position sensor and engine coolant temperature sensor
Frequency of Operation	Once per driving cycle

TYPICAL ENABLING CONDITIONS

Battery voltage	11 V or higher
Intake air temperature	-10°C (14°F) or higher
Engine coolant temperature	75°C (167°F) or higher
Atmospheric pressure	76 kPa (570 mmHg) or higher
Idling	OFF
Engine speed	Less than 4000 rpm
Air fuel ratio sensor status	Activated
Fuel system status	Closed loop
Engine load	10 to 80%
All of following conditions (a), (b) and (c) met	-
(a) Mass air flow	2.5 to 42 gm/s
(b) Estimated front catalyst temperature	685 to 800°C (1265 to 1472°F)
(c) Estimated rear catalyst temperature	400 to 800°C (752 to 1472°F)
Transmission gear	4th or higher

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.

Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the intelligent tester on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).
Turn the ignition switch off and wait for at least 30 seconds.
Turn the ignition switch to ON and turn the intelligent tester 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 (38 mph) for 10 minutes or more [B].
HINT:
Drive the vehicle while keeping the engine load as constant as possible.
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
Enter the following menus: Powertrain / Engine and ECT / DTC [C].
Read the pending DTCs.
HINT:
1. If a pending DTC is output, the system is malfunctioning.
2. If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0420.
Check the DTC judgment result.

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.

(a) Connect the intelligent tester 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 then 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the intelligent tester.

HINT:

If the voltage output of either the air fuel ratio or heated oxygen sensor does not fluctuate, or there is 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 intelligent tester.
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).

Result of Real-vehicle Check
Engine Speed	3000 rpm (without load)	2000 rpm (during fuel-cut)	2000 rpm (revving up the engine)
AFS Voltage B1S1	3.263 to 3.302 V	4.996 V	3.195 V
O2S B1S2	0.820 to 0.835 V	0.015 V	0.820 V

INSPECTION PROCEDURE

HINT:

Read freeze frame data using the intelligent tester. 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.
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)

Connect the intelligent tester to the DLC3.

Turn the ignition switch to ON.

Turn the intelligent tester on.

Enter the following menus: Powertrain / Engine and ECT / DTC.

Read the DTCs.
Result
Result
Proceed to
P0420 is output
A
P0420 and other DTCs are output
B
HINT:
If any DTCs other than P0420 are output, troubleshoot those DTCs first.

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

GO TO DTC CHART (HILUX_TGN26 RM0000032SF022X.html)

A

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

Connect the intelligent tester to the DLC3.

Start the engine.

Turn the intelligent tester 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 for A/F Sensor operation with the engine idling.

Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the intelligent tester.

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.

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

Result
Status of AFS Voltage B1S1	Status of O2S B1S2	Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensor Condition	Misfire	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	May occur	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 for A/F Sensor 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 for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently below 3.1 V, and the heated oxygen sensor voltage (O2S) is consistently higher than 0.55 V.
Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternate correctly.

HINT:

Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2] (HILUX_TGN26 RM000000SXS056X.html).

Go to step 5

Go to step 6

Go to step 8

A

3.CHECK FOR EXHAUST GAS LEAK

Inspect for exhaust gas leaks from the exhaust manifold and exhaust pipes.
OK:
No gas leaks.

REPAIR OR REPLACE EXHAUST GAS LEAK POINT

OK

4.REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST)

NOTICE:

Replace the front catalyst and rear catalyst together when catalyst replacement is necessary.

HINT:

Refer to the illustration in Catalyst Location to confirm which parts to replace.

Replace the front exhaust pipe assembly (HILUX_TGN26 RM00000135901FX.html).

END

5.REPLACE AIR FUEL RATIO SENSOR

Replace the air fuel ratio sensor (HILUX_TGN26 RM00000142300YX.html).

Go to step 10

6.CHECK FOR EXHAUST GAS LEAK

Inspect for exhaust gas leaks from the exhaust manifold and exhaust pipes.
OK:
No gas leaks.

REPAIR OR REPLACE EXHAUST GAS LEAK POINT

OK

7.REPLACE HEATED OXYGEN SENSOR

Replace the heated oxygen sensor (HILUX_TGN26 RM00000159M00IX.html).

Go to step 10

8.CHECK FOR EXHAUST GAS LEAK

Inspect for exhaust gas leaks from the exhaust manifold and exhaust pipes.
OK:
No gas leaks.

REPAIR OR REPLACE EXHAUST GAS LEAK POINT

OK

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

Check the cause of the extremely rich or lean actual air fuel ratio while referring to the DTC P0171 Inspection Procedure (HILUX_TGN26 RM000000WC30JOX_07.html).

NEXT

10.CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

Connect the intelligent tester to the DLC3.

Turn the ignition switch to ON.

Turn the intelligent tester on.

Clear the DTCs (HILUX_TGN26 RM000000PDK0SXX.html).

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

Turn the ignition switch to ON.

Turn the intelligent tester 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 / DTC.

Read the DTCs.
Result
Result
Proceed to
P0420 is output
A
No DTC is output
B
HINT:
If any DTCs other than P0420 are output, troubleshoot those DTCs first.

END

A

11.REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST)

NOTICE:

Replace the front catalyst and rear catalyst together when catalyst replacement is necessary.

HINT:

Refer to the illustration in Catalyst Location to confirm which parts to replace.

Replace the front exhaust pipe assembly (HILUX_TGN26 RM00000135901FX.html).

END