karnovking

My 01 Odyessy is reading code PO420 Catalyst system efficency below threshold.

Can someone tell me what this means?

somick

In the chart I have it says that the associated monitor is:

Catalytic converter monitor

Could it be just oxygen sensor?

Sam

__________________

Quote:

Originally Posted by RIP Please post back when you fix it so we all will learn something

karnovking

I cleared the code about 500 miles ago. it has yet to come back. so for now I'm not worrying about it.

I hope it is just the sensor(s)

wreckchord

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check [COLOR=#009600 ! important][COLOR=#009600 ! important]Engine [COLOR=#009600 ! important]Light[/color][/color][/color]
if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

wreckchord

Some suggested steps for troubleshooting a P0420 code include:

• Check for [COLOR=#009600 ! important][COLOR=#009600 ! important]exhaust[/color][/color]
  leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer [COLOR=#009600 ! important][COLOR=#009600 ! important]car[/color][/color] but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.