P0420
TECHNICAL DESCRIPTION- The signal from the rear heated oxygen sensor differs from the front heated oxygen sensor. That is because the catalytic converter purifies exhaust gas. When the catalytic converter has deteriorated, the signal from the front heated oxygen sensor becomes similar to the rear heated oxygen sensor.
- The PCM compares the output of the front and rear heated oxygen sensor signals.
DTC SET CONDITIONS
Check Conditions
- Engine speed is lower than 3,000 r/min.
- Volume air flow sensor output frequency is between 69 and 169 Hz.
- Intake air temperature is higher than -10 °C (14 °F).
- Barometric pressure is higher than 76 kPa (11 psi).
- The throttle valve is open.
- In closed loop.
- Vehicle speed is 1.5 km/h (0.93 mph) or more.
- Monitoring time: 84 seconds.
Judgment Criteria
- The heated oxygen sensor (rear) signal and heated oxygen sensor (front) signal are similar.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Right bank side catalytic converter deteriorated.
- Right bank heated oxygen sensor failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
STEP 1. Check the exhaust leakage.
1. Are there any cracks, etc., in the exhaust manifold and front exhaust pipe?
If no, go to Step 2.
If yes, repair or replace. Then go to Step 7.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 2. Using scan tool MB991502, check data list item 59: Heated Oxygen Sensor (rear).
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 69, Heated Oxygen Sensor (rear).
4. Run in L range at wide open throttle.
- The output voltage should between 0.6 and 1.0 volt after the engine is warmed.
If within specifications, go to Step 3.
If not within specifications, refer to DTC P0136 - O2 Sensor Circuit Malfunction (Sensor 2)
STEP 3. Using scan tool MB991502, check data list item 11: Heated Oxygen Sensor (front).
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 11, Heated Oxygen Sensor (front).
- Warm up the engine. When the engine is decelerated suddenly from 4000 r/min, the output voltage should increase from 200 mV or less to 600 - 1000 mV in a few seconds.
If within specifications, go to Step 4.
If not within specifications, refer to DTC P0130 - O2 Sensor Circuit Malfunction (Sensor 1)
STEP 4. Using scan tool MB991502, check data list item 11: Heated Oxygen Sensor (front).
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 11, Heated Oxygen Sensor (front).
3. Keep the engine speed at 2,000 r/min.
- 0 - 0.4 and 0.6 - 1.0 volt should alternate 5 times or more within 10 seconds.
If within specifications, replace the heated oxygen sensor (rear). Then go to Step 5.
If not within specifications, replace the heated oxygen sensor (front). Then go to Step 7.
STEP 5. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern.
Refer to Procedure 3 - Catalytic Converter Monitor.
2. Read the diagnostic trouble code (DTC).
If DTC P0420 is output, replace the catalytic converter. Then go to Step 6.
If DTC P0420 is not output, the inspection is complete.
STEP 6. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern.
Refer to Procedure 3 - Catalytic Converter Monitor.
2. Read the diagnostic trouble code (DTC).
If DTC P0420 is output, replace the PCM. Then go to Step 7.
If DTC P0420 is not output, the inspection is complete.
STEP 7. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern.
Refer to Procedure 3 - Catalytic Converter Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0420 does not reset.