NOx Sensor 1/2 Correlation Bank 1

Where it lives

For P221A, the part to look at first is the sensor named here. The description of P221A puts it on bank 1.

Check these first

• A bank 1 upstream NOx sensor and downstream sensor disagreeing
• A failed bank 1 NOx sensor reading off from its pair
• An exhaust leak between the bank 1 NOx sensors
• A restricted bank 1 exhaust component skewing one sensor

What to do next

1. Read both bank 1 NOx sensor signals on a scan tool
2. Compare the bank 1 NOx sensor readings to each other
3. Check the bank 1 exhaust between the sensors for leaks
4. Inspect the bank 1 exhaust for a restriction
5. Replace the bank 1 NOx sensor that reads out of step if the exhaust tests good
6. Clear the code and retest

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