P0420

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

MONITOR DESCRIPTION

DTC Detection Condition:

The ECM uses the heated oxygen sensors 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 2 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 heated oxygen sensor (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 length of the heated oxygen sensor (sensor 1) and heated oxygen sensor (sensor 2). The ECM calculates the rate of the signal length of the heated oxygen sensor (sensor 1) and heated oxygen sensor (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 (ECT) is 75 °C (167 °F) or more).
- The vehicle is driven at approximately 60 to 100 km/h (37 to 63 mph) for 15 minutes.

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunctions Thresholds:

MONITOR DESCRIPTION

MONITOR RESULT

Refer to CHECKING MONITOR STATUS. Mode 6 Data


CONFIRMATION DRIVING PATTERN




a. Connect the intelligent tester to the CAN VIM. Then connect the CAN VIM to the DLC3.
b. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / O2S B1S1 (or B2S1).
c. Start the engine and warm it up with all the accessories switched OFF until the ECT becomes stable.
d. 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.

e. Confirm that heated oxygen sensor (bank 1 sensor 1 (OX1A) and bank 2 sensor 1 (OX2A)) have waveforms that are around 0.5 V during feedback to the ECM. Then check the waveform of the heated oxygen sensor (bank 1 sensor 2 (OX1B) and bank 2 sensor 2 (OX2B)) for the same waveforms (0.5 V during feedback).






HINT: If there is a malfunction in the catalyst, the waveform of the heated oxygen sensor (sensor 2) (OX1B, OX2B) is almost the same as that of the heated oxygen sensor (sensor 1) (OX1A, OX2A), which is shown.

Wiring Diagram:

Step 1-2:

Step 3-4:

Step 4(Continued)-5:

Step 5(Continued):

INSPECTION PROCEDURE

HINT:
- Read freeze frame data using the intelligent 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.
- If DTC P0420 is displayed, check the bank 1 catalyst.
- If DTC P0430 is displayed, check the bank 2 catalyst.
- Bank 1 includes No. 1 cylinder, but bank 2 does not. No. 1 cylinder is located in the front part of the engine, opposite the transmission.