SFI SYSTEM, Diagnostic DTC:P042000

DTC Code	DTC Name
P042000	Catalyst System Efficiency Below Threshold Bank 1

MONITOR DESCRIPTION

w/ Differential Pressure Sensor

The ECM uses air fuel ratio 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 (sensor 1), sends pre-catalyst information to the ECM. The second sensor, the air fuel ratio sensor (sensor 2), 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 air fuel ratio sensor (sensor 2) while performing active air fuel ratio control.

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 30 seconds. When it is performed, the ECM deliberately sets the air fuel ratio to lean or rich levels. If the cycle of the waveform for the air fuel ratio sensor (sensor 2) is long, the oxygen storage capacity is great. There is a direct correlation between the air fuel ratio sensor (sensor 2) and the oxygen storage capacity of 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, the ECM will illuminate the MIL and store a DTC.

This system determines the deterioration of the entire catalyst system (including the front and rear catalysts), by using the oxygen storage capacity value of the front catalyst, that is more sensitive than the rear catalyst, as the representative value. Therefore, be sure to replace the front and rear catalysts together when catalyst replacement is necessary.

w/o Differential Pressure Sensor

The ECM uses air fuel ratio 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, 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.

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 30 seconds. When it is performed, the ECM deliberately sets the air fuel ratio to lean or rich levels. If the cycle of the waveform for the heated oxygen sensor is long, the oxygen storage capacity is great. There is a direct correlation between the heated oxygen sensor and the oxygen storage capacity of 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, the ECM will illuminate the MIL and store a DTC.

This system determines the deterioration of the entire catalyst system (including the front and rear catalysts), by using the oxygen storage capacity value of the front catalyst, that is more sensitive than the rear catalyst, as the representative value. Therefore, be sure to replace the front and rear catalysts together when catalyst replacement is necessary.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P042000	Catalyst System Efficiency Below Threshold Bank 1	The oxygen storage capacity value is less than the standard value under active air fuel ratio control (2 trip detection logic).	w/ Differential pressure sensor Gas leak from exhaust system Air fuel ratio sensor (sensor 1) Air fuel ratio sensor (sensor 2) Converter assembly (TWC: Front catalyst) Front exhaust pipe assembly (TWC: Rear catalyst) w/o Differential pressure sensor Gas leak from exhaust system Air fuel ratio sensor (sensor 1) Heated oxygen sensor Exhaust manifold converter sub-assembly (TWC: Front catalyst) and front exhaust pipe assembly (TWC: Rear catalyst)	Comes on (Euro-OBD) / - (Except Euro-OBD)	DTC stored (Euro-OBD) / - (Except Euro-OBD)	SAE Code: P0420

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P042000

Catalyst System Efficiency Below Threshold Bank 1

The oxygen storage capacity value is less than the standard value under active air fuel ratio control (2 trip detection logic).

w/ Differential pressure sensor

Gas leak from exhaust system
Air fuel ratio sensor (sensor 1)
Air fuel ratio sensor (sensor 2)
Converter assembly (TWC: Front catalyst)
Front exhaust pipe assembly (TWC: Rear catalyst)

w/o Differential pressure sensor

Gas leak from exhaust system
Air fuel ratio sensor (sensor 1)
Heated oxygen sensor
Exhaust manifold converter sub-assembly (TWC: Front catalyst) and front exhaust pipe assembly (TWC: Rear catalyst)

Comes on (Euro-OBD) / - (Except Euro-OBD)

DTC stored (Euro-OBD) / - (Except Euro-OBD)

SAE Code:

P0420

CATALYST LOCATION

w/ Differential Pressure Sensor

*A	for 2WD	-	-
*1	Air Fuel Ratio Sensor (Sensor 1)	*2	Exhaust Manifold Converter Sub-assembly (TWC: Front Catalyst)
*3	Front Exhaust Pipe Assembly (TWC: Rear Catalyst)	*4	Air Fuel Ratio Sensor (Sensor 2)
*5	Tail Exhaust Pipe Assembly	-	-

*A	for AWD	-	-
*1	Air Fuel Ratio Sensor (Sensor 1)	*2	Exhaust Manifold Converter Sub-assembly (TWC: Front Catalyst)
*3	Front Exhaust Pipe Assembly	*4	Air Fuel Ratio Sensor (Sensor 2)
*5	Front Exhaust Pipe Assembly (TWC: Rear Catalyst)	*6	Tail Exhaust Pipe Assembly

w/o Differential Pressure Sensor

*A	for 2WD	-	-
*1	Air Fuel Ratio Sensor (Sensor 1)	*2	Exhaust Manifold Converter Sub-assembly (TWC: Front Catalyst)
*3	Front Exhaust Pipe Assembly (TWC: Rear Catalyst)	*4	Heated Oxygen Sensor
*5	Tail Exhaust Pipe Assembly	-	-

*A	for AWD	-	-
*1	Air Fuel Ratio Sensor (Sensor 1)	*2	Exhaust Manifold Converter Sub-assembly (TWC: Front Catalyst)
*3	Front Exhaust Pipe Assembly	*4	Heated Oxygen Sensor
*5	Center Exhaust Pipe Sub-assembly (TWC: Rear Catalyst)	*6	Tail Exhaust Pipe Assembly

Note

w/ Differential Pressure Sensor

Replace the exhaust manifold converter sub-assembly (*2) and the front exhaust pipe assembly (*3) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor (sensor 1)*1 and air fuel ratio sensor (sensor 2)*4)

w/o Differential Pressure Sensor

Replace the exhaust manifold converter sub-assembly (*2) and the front exhaust pipe assembly (*3) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor (sensor 1)*1 and heated oxygen sensor*4)

MONITOR STRATEGY

w/ Differential Pressure Sensor
Required Sensors/Components (Main)	Air fuel ratio sensor (sensor 1) Air fuel ratio sensor (sensor 2)
Required Sensors/Components (Related)	Intake air temperature (mass air flow meter) Mass air flow meter Crankshaft position sensor Engine coolant temperature sensor
Frequency of Operation	Once per driving cycle

w/o Differential Pressure Sensor
Required Sensors/Components (Main)	Air fuel ratio sensor Heated oxygen sensor
Required Sensors/Components (Related)	Intake air temperature sensor (mass air flow meter) Mass air flow meter Crankshaft position sensor Engine coolant temperature sensor
Frequency of Operation	Once per driving cycle

TYPICAL ENABLING CONDITIONS

w/ Differential Pressure Sensor
Response rate during fuel cut from rich condition	Completed
Battery voltage	11 V or higher
Intake air temperature (mass air flow meter sub-assembly)	-10°C (14°F) or higher
Engine coolant temperature	75°C (167°F) or higher
Atmospheric pressure	76 kPa(abs) [11 psi(abs)] or higher
Idling	Off
Engine speed	Less than 4000 rpm
Sub feedback control	Executing
Air fuel ratio sensor (sensor 1) status	Activated
Fuel system status	Closed loop
Engine load	10% or higher, and less than 140%
All of the following conditions are met	1, 2 and 3
1. Mass air flow	6.0 gm/sec or more, and less than 40 gm/sec
2. Front catalyst temperature (estimated)	570°C (1058°F) or higher, and less than 800°C (1472°F)
3. Rear catalyst temperature (estimated)	460°C (860°F) or higher, and less than 700°C (1292°F)

w/o Differential Pressure Sensor
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(abs) [11.02 psi(abs)] or higher
Idling	Off
Engine speed	Less than 4000 rpm
Air fuel ratio sensor status	Activated
Fuel system status	Closed loop
Engine load	10% or higher, and less than 140%
All of the following conditions are met	-
Mass air flow rate	6.0 to 40 gm/sec.
Front catalyst temperature (estimated)	570°C (1058°F) to 800°C (1472°F)
Rear catalyst temperature (estimated)	460°C (860°F) to 700°C (1292°F)

CONFIRMATION DRIVING PATTERN

Tech Tips

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

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the ignition switch off and wait for at least 30 seconds.
Turn the ignition switch to ON.
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.

Tech Tips

Drive the vehicle while keeping the engine load as constant as possible.
Turn the ignition switch off and wait for at least 30 seconds [C].
Turn the ignition switch to ON.
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.

Tech Tips

Drive the vehicle while keeping the engine load as constant as possible.
Enter the following menus: Powertrain / Engine / Trouble Codes [F].
Read the pending DTCs.
Tech Tips
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P042000.

Check the DTC judgment result.

GTS Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

Tech Tips

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A and no pending DTC is output, perform the following procedure.

Drive the vehicle at a speed between 75 and 100 km/h (47 and 62 mph) for 10 minutes or more [G].

CAUTION:

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

Tech Tips

Drive the vehicle while keeping the engine load as constant as possible.
Enter the following menus: Powertrain / Engine / Trouble Codes [H].
Read the pending DTCs.
Tech Tips
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P042000.

Check the DTC judgment result.

GTS Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

Tech Tips

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform the Confirmation Driving Pattern and check the DTC judgment result again.

CONDITIONING FOR SENSOR TESTING

w/o Differential Pressure Sensor:

Tech Tips

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 GTS to the DLC3.
(b) Start the engine and warm it up with all the accessories switched off until the engine coolant temperature stabilizes.
(c) Enter the following menus: Powertrain / Engine / Data List / All Data / A/F (O2) Sensor Voltage B1S1 and O2 Sensor Voltage B1S2.
(d) Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes.
(e) 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.

Tech Tips

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).

CAUTION / NOTICE / HINT

Tech Tips

If a malfunction cannot be found when troubleshooting DTC P042000, a lean or rich abnormality may be the cause. Perform troubleshooting by following the inspection procedure for P017100 (System Too Lean) and P017200 (System Too Rich).
Read freeze frame data using the GTS. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P042000)

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Read the DTCs.

Result

Result	Proceed to
DTC P042000 is output (w/ Differential pressure sensor)	A
DTC P042000 is output (w/o Differential pressure sensor)	B
DTC P042000 and other DTCs are output	C

Tech Tips

If any DTCs other than P042000 are output, troubleshoot those DTCs first.

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) Click here

GO TO DTC CHART Click here

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.
Warm up the air fuel ratio sensors at an engine speed of 2500 rpm for 90 seconds.

Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / Data List / A/F (O2) Sensor Current B1S1 and A/F (O2) Sensor Current B1S2.

Powertrain > Engine > Active Test

Active Test Display
Control the Injection Volume for A/F Sensor

Data List Display
A/F (O2) Sensor Current B1S1
A/F (O2) Sensor Current B1S2

Change the fuel injection volume using the GTS, and monitor the output current of the air fuel ratio sensor (sensor 1) (A/F (O2) Sensor Current B1S1 and air fuel ratio sensor (sensor 2) (A/F (O2) Sensor Current B1S2 displayed on the GTS.

Tech Tips

The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.
The air fuel ratio sensor (sensor 1) is displayed as A/F (O2) Sensor Current B1S1 and the air fuel ratio sensor (sensor 2) is displayed as A/F (O2) Sensor Current B1S2 on the GTS.
The air fuel ratio sensor (sensor 1) has an output delay of a few seconds and the air fuel ratio sensor (sensor 2) has a maximum output delay of approximately 20 seconds.
If the sensor output current does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

Standard

GTS Display (Sensor)	Injection Volume	Status	Voltage
A/F (O2) Sensor Current B1S1 (Air fuel ratio (sensor 1))	12.5%	Rich	Below -0.075 mA
A/F (O2) Sensor Current B1S1 (Air fuel ratio (sensor 1))	-12.5%	Lean	More than 0.037 mA
A/F (O2) Sensor Current B1S2 (Air fuel ratio (sensor 2))	12.5%	Rich	Below -0.86 mA
A/F (O2) Sensor Current B1S2 (Air fuel ratio (sensor 2))	-12.5%	Lean	More than 0.33 mA

Result

Status of A/F (O2) Sensor Current B1S1	Status of A/F (O2) Sensor Current B1S2	Actual air fuel ratio, air fuel ratio sensor (sensor 1) and air fuel ratio sensor (sensor 2) condition	Main Suspected Trouble Area	Proceed to
Lean/Rich	Lean/Rich	Normal	Three-way catalytic converter Gas leak from exhaust system	A
Lean	Lean/Rich	Air fuel ratio sensor (sensor 1) malfunction	Air fuel ratio sensor (sensor 1)	B
Rich	Lean/Rich	Air fuel ratio sensor (sensor 1) malfunction	Air fuel ratio sensor (sensor 1)	B
Lean/Rich	Lean	Air fuel ratio sensor (sensor 2) malfunction	Air fuel ratio sensor (sensor 2) Gas leak from exhaust system	C
Lean/Rich	Rich	Air fuel ratio sensor (sensor 2) malfunction	Air fuel ratio sensor (sensor 2) Gas leak from exhaust system	C
Lean	Lean	Actual air fuel ratio lean	Extremely lean actual air fuel ratio Gas leak from exhaust system	D
Rich	Rich	Actual air fuel ratio rich	Extremely rich actual air fuel ratio Gas leak from exhaust system	D

Lean: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (A/F (O2) Sensor Current B1S1 is consistently more than 0.037 mA, and the air fuel ratio sensor (sensor 2) output current (A/F (O2) Sensor Current B1S2 is consistently more than 0.33 mA.
Rich: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (A/F (O2) Sensor Current B1S1 is consistently below -0.075 mA, and the air fuel ratio sensor (sensor 2) output current (A/F (O2) Sensor Current B1S2 is consistently below -0.86 mA.
Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output current of the air fuel ratio sensor (sensor 1) or air fuel ratio sensor (sensor 2) alternate correctly.

Tech Tips

Refer to "Data List / Active Test" [A/F (O2) Sensor Current B1S1, A/F (O2) Sensor Current B1S2.

Click here

REPLACE AIR FUEL RATIO SENSOR (SENSOR 1) Click here

CHECK FOR EXHAUST GAS LEAK Click here

CHECK FOR EXHAUST GAS LEAK

Check for exhaust gas leaks.

OK
No gas leaks.

Result

Proceed to
OK
NG

GO TO STEP 17 Click here

GO TO STEP 9 Click here

REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)

Replace the air fuel ratio sensor (sensor 1).