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I have 2013 LML with no engine mods and I’m getting a P11A9 code. The code will populate for up for a week or so and then go away for a day or so and then come back. Truck runs great but I have an emissions test soon and need to get this squared away. I can’t find anything online on this so I’m looking for help.

The code reads P11A9- HO2S signal low during moderate load sensor 1.
 

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Do you have an aftermarket intake? I’m seeing that it’s a NOX sensor 1 faulty


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