P0420

1NZ-FXE 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 2 sensors mounted before and after the three-way catalytic converter (TWC) to monitor its efficiency. The air-fuel ratio (A/F) sensor (sensor 1) sends pre-catalyst information to the ECM. The heated oxygen (HO2) sensor (sensor 2) sends post-catalyst information to the ECM.
In order to detect deterioration in the catalyst, the ECM calculates Oxygen Storage Capacity (OSC) in the catalyst based on voltage output of sensor 2 while performing "active air-fuel ratio control" instead of the conventional detecting method which uses the locus ratio.
The OSC is an indication value of the catalyst oxygen storage capacity and is used for representing how much the catalyst can store oxygen. When the vehicle is being driven with a warm engine, the active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the air-fuel ratio is forcibly regulated to be LEAN or RICH by the ECM, and if a RICH and LEAN cycle of sensor 2 is long, the OSC will become greater. The greater OSC and capability of the catalyst are mutually related. The ECM judges if the catalyst has deteriorated based on the calculated OSC value. The ECM will illuminate the MIL and a DTC will be set.





HINT:
- Sensor 1 refers to the sensor mounted before the TWC and is located near the engine assembly.
- Sensor 2 refers to the sensor mounted after the TWC and is located far from the engine assembly.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to detailed information Mode 6 Data.

CONFIRMATION DRIVING PATTERN
- PURPOSE Monitors, Trips, Drive Cycles and Readiness Codes
HINT: Performing this confirmation pattern will activate the catalyst monitoring by the ECM. This is very useful for verifying the completion of repairs.





(a) Clear the DTCs DTC Check / Clear.
(b) Connect Techstream to the DLC3.
(c) Enter the following menus: Powertrain / Engine and ECT / Monitor. Check that Catalyst Efficiency is incomplete.
(d) Drive the vehicle according to the confirmation driving pattern. Note the state of the Readiness Tests. They will change to complete as the Catalyst Efficiency evaluation monitors operate.
(e) Enter the following menus: Powertrain / Engine and ECT / Trouble Code / Pending. Check if any DTC (any pending code) is set.
If the READINESS CODE of Catalyst Efficiency was incomplete and any DTC (includes pending codes) was not set, extend the driving time.
NOTE: If you do not have Techstream, perform again the same confirmation driving pattern after turning OFF the power switch upon finishing the first confirmation driving pattern.

CONDITIONING FOR SENSOR TESTING





(a) Connect Techstream to the DLC3.
(b) Put the engine in inspection mode Service Precautions.
(c) Start the engine and warm it up with all the accessories switched OFF until the engine coolant temperature becomes stable.
(d) Run the engine at 2,500 rpm for approximately 3 minutes.
(e) Run the engine at 2,500 rpm for 2 seconds and then 1,500 rpm for 2 seconds.
(f) Check the waveform of the oxygen sensor (sensor 2).
HINT: If output of the A/F sensor or the heated oxygen sensor does not fluctuate or has noise, the sensor may be malfunctioning.
If voltage output of both sensors remain at LEAN or RICH, the air-fuel ratio may be extremely LEAN or RICH. In such a case, perform the following Control the Injection Volume for A/F Sensor operation in Active Test using Techstream. If the catalyst has deteriorated, the voltage output of the heated oxygen sensor fluctuates up and down widely even under normal driving ("active air-fuel ratio control" is not performed).





INSPECTION PROCEDURE
HINT:
- Read freeze frame data using 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.
- Malfunctioning areas can be found by performing the Control the Injection Volume for A/F Sensor operation. The Control the Injection Volume for A/F Sensor operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble area are malfunctioning or not.
(a) Perform the Control the Injection Volume for A/F Sensor operation.
- The Control the Injection Volume for A/F Sensor operation lowers the injection volume 12.5% or increases the injection volume 25%.
(1) Connect Techstream to the DLC3.
(2) Turn the power switch ON (IG).
(3) Put the engine in inspection mode Service Precautions.
(4) Warm up the engine by running the engine at 2,500 rpm, depressing the accelerator pedal more than 60% for approximately 90 seconds.
(5) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
(6) Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idle condition (press the right or left button).
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25% = rich output: Less than 3.1 V
-12.5% = lean output: More than 3.4 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25% = rich output: More than 0.55 V
-12.5% = lean output: Less than 0.4 V
NOTE: The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.





The following Control the Injection Volume for A/F Sensor procedure enables the technician to check and graph the voltage output of both A/F sensor and heated oxygen sensor.
To display the graph, enter Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 and O2S B1 S2 then press the graph button on the Data List view.

PROCEDURE

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0420)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn Techstream ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:





HINT: If any other codes besides P0420 are output, perform troubleshooting for those DTCs first.

B -- GO TO DTC CHART
A -- Continue to next step.

2. PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL)
(a) Connect Techstream to the DLC3.
(b) Put the engine in inspection mode Service Precautions.
(c) Turn the tester on.
(d) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(e) On the tester, select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
(f) 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).
(g) Monitor the voltage outputs of the A/F and HO2 sensors (AFS Voltage B1 S1 and O2S B1 S2) displayed on the tester.
Result:
A/F sensor reacts in accordance with increases and decreases in fuel injection volume:
+25% = Rich output
Less than 3.0 V
-12.5% = Lean output
More than 3.35 V
NOTE: The A/F sensor has an output delay of a few seconds and the 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 on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 and O2S B1 S2 then press the graph button on the Data List view.

Result:






D -- CHECK AND REPAIR CAUSES OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO, AND GO TO STEP 3
C -- INSPECT FOR EXHAUST GAS LEAK
B -- REPLACE AIR FUEL RATIO SENSOR
A -- Continue to next step.

3. INSPECT FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leakage.
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- REPLACE FRONT EXHAUST PIPE ASSEMBLY
4. INSPECT FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leakage.
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- REPLACE HEATED OXYGEN SENSOR