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How do you turn off rear O2 sensor and catalytic converter codes?

In the calibration. Swap calibrations commonly set the post-catalyst O2 and catalyst diagnostics to match what's installed (GM Truck Central, Chevy Hardcore). Retailer-programmed 0411/P59 swap units usually arrive with rear O2 diagnostics already disabled (Warr Performance). Many standalone swap harnesses don't wire the rear O2 sensors at all (Speedway).

Check your local emissions rules before removing cats on a street vehicle. See the swap tune checklist.

More: who tunes it, and how to learn.

Confidence: medium — sources disagree or are limited; check the sources below.

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