Generic (OBD-II) interpretation in the TuningBot DTC database.
P · PowertrainEmissionsOBD2
What P221A means
P221A
NOx Sensor 1/2 Correlation Bank 1
Generic · emissions
Data confidence65%
The control module detected a fault associated with the NOx Sensor 1/2 Correlation Bank 1 circuit or function; the stored code identifies the affected component rather than a single failure mode.
Symptoms
MIL or SCR/AdBlue warning illuminated
Possible start-count-down or torque limitation on some applications
Possible causes
Reductant quality or level fault
Dosing valve or supply module fault
NOx sensor fault
Frozen or crystallized reductant lines
Wiring or connector fault
Recommended checks
Read NOx sensor values and dosing system status
Check reductant level and quality data
Inspect dosing valve, lines and heater operation
Check wiring and connectors of the SCR components
Check for OEM technical bulletins and software updates
Powertrain: engine, transmission and driveline systems.
2
Generic SAE-standard code: same meaning on every make.
21A
Specific fault index within the subsystem.
Frequently asked questions about P221A
What does P221A mean?
NOx Sensor 1/2 Correlation Bank 1. The control module detected a fault associated with the NOx Sensor 1/2 Correlation Bank 1 circuit or function; the stored code identifies the affected component rather than a single failure mode.
Is P221A generic or manufacturer-specific?
P221A is a generic OBD-II code: it has the same meaning on every make and model that follows the SAE standard.
Can TuningBot remove P221A at file level?
If the fault logic lives in the ECU calibration, yes: our DTC Removal file service disables the specific fault entry. Checksum correction is not included: it is a separate, optional service. Not sure whether your case qualifies? Request a free assessment and our engineers will check your ECU file.
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