Rick's Free Auto Repair Advice

Fix code P0430

Code P0430 Catalyst System Efficiency Below Threshold (Bank 2)

NOTE: Codes P0420 and code P0430 are similar. I wrote a much more detailed explanation of how an emission system works and what causes these codes. Read this post and then refer to this more detailed post.

Code P0430 means the catalytic converter for bank 2 has failed it’s testing. The oxygen sensor in front of the catalytic converter switches back and forth between rich and lean as the computer constantly changes air fuel mixture. If the catalytic converter is doing its job, downstream t oxygen sensor should not switch between rich and lean. If it does, that means the catalytic converter is NOT doing its job and the computer turn on the check engine light and set code P0430.

Catalytic converters generally do NOT fail on their own. They usually fail because of misfires that have not been repaired. That allows the engine to dump excess gas into the converter. The excess gas is burned off in the converter and causes internal core temperature to rise to the point of destroying the converter. All the precious metals melt. If you replace the catalytic converter but do NOT fix the underlying cause, you will be replacing the converter again and again.

Two things to check to determine if the catalytic converter is toast

First, use a scan tool with live data to check for high long term fuel trims. If long term fuel trims are excessively high, like 25% or more, the computer is flooding the engine with fuel and most of that fuel is loading the catalytic converter and causing the P0420 or P0430. If you find a high LT fuel trim, find the root cause and fix it.

Next, check for an exhaust leak. Outside air leaking into the exhaust can mess up the oxygen sensor readings. All you need to check for an exhaust leak is a shop vac, duct tape and a spray bottle of soapy water. See this article on how to do the test.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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