Cause
Purge cycles not completing
The regeneration or purge cycle of a NOx adsorber repeatedly failing to finish. The trap fills during normal running and is emptied by a brief rich excursion that converts the stored oxides; if that cycle does not complete, capacity is never recovered.
One incomplete cycle is not a fault — the process needs particular conditions and a journey that ends first will interrupt it. A pattern of them is, and the count of failed attempts is the number to read rather than the code itself.
Interruption divides into usage and inhibition, and they need separating. The journey ended, which is the owner's driving pattern; or the module aborted because a condition went out of range — temperature not reached, a sensor disagreeing, or another fault blocking it. The stored abort reason distinguishes them and is far more useful than the code. The consequence compounds, since a fuller trap makes the next cycle harder and more likely to be aborted.
Typically a moderate job.
Codes this can cause (2)
Codes where this is a likely explanation first, rather than merely a possible one.
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