P0430

DTC P0430 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 2)

CIRCUIT DESCRIPTION

The ECM uses sensors mounted before and after the three-way catalyst (TWC) to monitor its efficiency. The first sensor, an Air Fuel ratio (A/F) sensor 1, sends pre-catalyst A/F ratio information to the ECM. The second sensor, a heated oxygen sensor (02S), 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 below.

If the catalyst is functioning normally, the waveform of the heated oxygen sensor 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 monitor, the ECM compares sensor 1 signals (A/F sensor) over a specific amount of time to determine catalyst efficiency. The ECM begins by calculating the signal length for both sensors (for the rear oxygen sensor, the ECM uses the output voltage signal length). If the oxygen sensor output voltage signal length is greater than the threshold (threshold is calculated based on the A/F sensor signal length), the ECM concludes that the catalyst is malfunctioning. The ECM will turn on the MIL and a DTC will be set.














MONITOR STRATEGY







TYPICAL ENABLING CONDITIONS






TYPICAL MALFUNCTION THRESHOLDS






MONITOR RESULT (MODE 6)






CONFIRMATION DRIVING PATTERN

(a) Connect the hand-held tester to the DLC3.

(b) Clear DTC.

(c) Warm-up the engine.

(d) Drive the vehicle at 40 - 55 mph (64 - 88 km/h) for 4 minutes.

(e) Drive the vehicle allowing speed to fluctuate between 35 - 45 mph (56 - 72 km/h) for 16 minutes.

(f) Check pending DTC.

NOTICE:
Drive with smooth throttle operation and avoid sudden acceleration.






INSPECTION PROCEDURE

Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.