P0420 & P0430

One of the issues that will also trigger a P0430 is either a high or low voltage to the sensor. And, while this hasn't been mentioned yet, it's easy to check the wiring harness and connectors.
My JKU just had the top of the engine rebuilt with new lifters and cams, oil cooler, axle seals, differential gaskets, and a few other deferred maintenance items, etc. When the work was completed, it threw the code on its initial test drive. Checked the entire wiring harness, and double checked the sensor connections. Hooked it up to the shop scanner and let her run for a bit. Code cleared, then we went back and looked at the code history and the P0430 last showed up when I replaced the battery late last year. Once it cleared, probably after the ECM relearned everything, it's not been back.
 
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