P22FD
NOx Sensor Performance Slow Response High to Low Bank 1 Sensor 2
What it means
The downstream NOx sensor on bank 1 (post-SCR) responds too slowly when NOx levels fall after a reductant injection event. The control unit measures the time between commanded reductant dose and the resulting NOx drop and finds it exceeds the diagnostic threshold, indicating an aged sensor element.
Is it safe to drive?
This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly.
Most likely causes
NOx sensor element aged or thermally damaged
highOne of the most commonly reported causes for this code — check this first.
SCR efficiency reduced (catalyst aged or contaminated)
mediumA plausible cause — test and verify before replacing parts.
Reductant injector dosing drift
lowLess common, but worth ruling out after the more likely causes.
Related help
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