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Home >> Lexus >> 2007 >> LS 460 V8-4.6L (1UR-FSE) >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0420

P0420

DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)
DTC P0430 Catalyst System Efficiency Below Threshold (Bank 2)

DESCRIPTION

DTC Detection Condition:




Monitor Strategy:




Typical Enabling Conditions:




Typical Malfunction Thresholds:




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 (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air-fuel ratio control, rather than the conventional detecting method, which uses the locus ratio.

The OSC value is an indication of the oxygen storage capacity of the 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 a rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.

The ECM uses the OSC value to determine the state of the TWC. 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.

MONITOR RESULT

Refer to CHECKING MONITOR STATUS. Mode 6 Data

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 intelligent tester or Techstream to the DLC3.
b. Turn the engine switch on (IG).
c. Turn the tester ON.
d. Clear DTCs (if set).

e. Enter the following menus:
- Intelligent Tester - Select: DIAGNOSIS / CARB OBD II / READINESS TESTS.
- Techstream - Select: Powertrain / Engine / Utility.

f. Check that CAT EVAL*1 (Catalyst / Status2)*2 is INCMPL*1 (Incomplete)*2.
g. Start the engine and warm it up.
h. Drive the vehicle at between 40 mph and 70 mph (64 km/h and 113 km/h) for at least 10 minutes.
i. Those items will change to COMPL*1 (Complete)*2 as CAT EVAL*1 (Catalyst)*2 monitor operates.

j. On the tester, enter the following menus:
- Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES; then check if any DTCs (any pending DTCs) are set.
- Techstream - Select: Powertrain / Engine / Trouble Codes / Pending; then check if any DTCs (any pending DTCs) are set.

HINT:
- If CAT EVAL*1 (Catalyst)*2 does not change to COMPL*1 (Complete)*2, and any pending DTCs fail to set, extend the driving time.
- *1: Intelligent tester
- *2: Techstream

CONDITIONING FOR SENSOR TESTING

HINT: Perform the operation with the engine speeds and time durations described prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.




a. Connect the intelligent tester or 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 2500 rpm and 3000 rpm for at least 3 minutes.
d. While running the engine at 3000 rpm for 2 seconds and 2000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester.






HINT:
- If either of the voltage outputs of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) 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, perform the following menus:
a. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
b. Techstream - Select: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.

- If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).

Step 1:




Step 1(Continued)-2:




Step 2(Continued)-3:




INSPECTION PROCEDURE

HINT: Malfunctioning areas can be identified by performing the A/F CONTROL*1 (Control the Injection Volume for A/F sensor*2) function provided in the Active Test. The A/F CONTROL (Control the Injection Volume for A/F sensor) function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the A/F CONTROL (Control the Injection Volume for A/ F sensor) operation using the intelligent tester or Techstream.

*1: Intelligent tester
*2: Techstream

1. Connect the intelligent tester or Techstream to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

4. On the tester, enter the following menus:
a. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
b. Techstream - Select: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.

5. Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
6. Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.









HINT:
- The A/F CONTROL (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.






NOTE: The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.

- Following the A/F CONTROL or 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, enter the following menus:
1. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / A/F CONTROL SYS / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2; then press the YES button and the ENTER button followed by the F4 button.
2. Techstream - Select: 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 intelligent tester or Techstream. 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.
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