P0420
DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)
DTC Detection Condition:
HINT:
- If DTC P0420 is displayed, check the bank 1 catalyst.
- If DTC P0430 is displayed, check the bank 2 catalyst.
- Bank 1 includes cylinder No. 1, but bank 2 does not. Cylinder No. 1 is located in the front part of the engine, opposite the transmission.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
The ECM uses Heated Oxygen Sensor (HO2S) mounted before and after the Three-Way Catalyst (TWC) to monitor its' efficiency. The front sensor sends pre-catalyst air-fuel information to the ECM. The rear sensor sends post-catalyst information to the ECM. The ECM compares these two signals to judge the efficiency of the catalyst and the catalyst's ability to store oxygen. During normal operation, the TWC stores and releases oxygen as needed.The capacity to store oxygen results in a low variation in the post-TWC exhaust stream as shown.
If the catalyst is functioning normally, the waveform of the HO2S (sensor 2) slowly switches between RICH and LEAN. If the catalyst is deteriorated, the waveform will alternate frequently between RICH and LEAN. As the catalyst efficiency degrades, its ability to store oxygen is reduced and the catalyst output becomes more variable.
When running the catalyst monitor, the ECM begins to measure the signal lengths of the HO2S (sensor 1.and HO2S (sensor 2). The ECM calculates the rate of signal length of the HO2S (sensor 1.and HO2S (sensor 2) (catalyst deterioration level). If the catalyst deterioration level exceeds the threshold, the ECM interprets this as a catalyst malfunction. The ECM illuminates the MIL (2 trip detection logic) and sets a DTC.
The monitor runs after:
- The engine is warmed up (engine coolant temperature is 75 °C (167 °F) or more..
- Acceleration and deceleration are performed at approximately 60 km/h (37 mph) for 15 minutes.
MONITOR RESULT
Refer to Monitor Trips and/or Drive Cycle.
The test value and test limit information are described as shown in the table.Check the monitor result and test values after performing the monitor drive pattern.
- TID (Test Identification Data. is assigned to each emissions-related component.
- TLT (Test Limit Type.: If TLT is 0, the component is malfunctioning when the test value is higher than the test limit. If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
- CID (Component identification Data. is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD II scan tools.
CONFIRMATION DRIVING PATTERN
a. Connect the hand-held tester to the DLC3.
b. Start the engine and warm it up with all the accessories switched OFF until the ECT becomes stable.
c. Run the engine at 2,500 to 3,000 rpm for about 3 minutes.
HINT: Control the engine RPM so that the calculated catalyst temperature can be between 550 and 800 °C (1,022 and 1,472 °F). The calculated catalyst temperatures of bank 1 and bank 2 can be read by viewing CAT TEMP B1S1 and CAT TEMP B2S1 of the DATA LIST.
d. Confirm that HO2S (bank 1 sensor 1 (OXL1.and bank 2 sensor 1 (OXR1.) have waveforms that are around 0.5 V during feedback to the ECM. Then check the waveform of HO2S (bank 1 sensor 2 (OXL2.and bank 2 sensor 2 (OXR2.) for the same waveforms (0.5 V during feedback).
HINT: If there is a malfunction in the catalyst, the waveform of the HO2S (sensor 2.(OXL1, OXR1.is almost the same as that of the HO2S (sensor 1.(OXL2, OXR2.
Wiring Diagram:
Step 1 - 2:
Step 3:
Step 4:
Step 4(contd.):
INSPECTION PROCEDURE
HINT: Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when a malfunction is detected.When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.