P0430 Catalyst System Efficiency Below Threshold



The other day the engine light came on in the 2008 H3 Hummer Alpha with the 5.3L V8. I took out my handy scan tool and checked the error code with the Android App Torque Pro to see what’s up.

Fault code: P0430 Catalyst System Efficiency Below Threshold (Bank 2)

After some Google-ing, I found a lot of people on the Hummer Forums immediately changing out the catalytic converter. I’ve never had a bad catalytic converter on any of the vehicles owned. However, I have replaced a bunch of 02 sensors over the years. This is why I choose to have Rockauto.com ship a brand new downstream 02 sensor to my door for $50, rather than immediately replacing one of the $300 catalytic converters. I even read about a K&N air filter possible causing the P0430 engine code.

Hopefully, the engine code is just a simple fix, I’ll report back.

  1. Drew Jarrett Avatar

    Any changes or updates since replacing the O2 sensor?

    1. Schwarttzy Avatar

      I’ve come to the conclusion that the passenger side catalytic converter is bad. The aftermarket ones I’ve tried to purchase are very poorly made. I hope to purchase an OEM cat soon. I’ll be sure to post up when install the cat.

      1. Schwarttzy Avatar

        New update, on trip back from Texas to Illinois the water pump failed. The water pump was replaced along with the thermostat and the GM Dealer reset the ECU. I’ve driven a bit over 600+ miles so far and I haven’t had the engine light come back on. I feel as though ECU light should have reappear by now the catalytic converter. Which is why I’m thinking the engine temps were messing with the ECU that may have caused the P0430 code.

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