Emissions

P2220 — NOx Sensor Current Low (Bank 1 Sensor 1)

Severity: medium Drive with care, to a shop

What P2220 means

The NOx sensor in the exhaust measures nitrogen oxides (and oxygen) through the current in its sensing cells, and the ECU uses this to run the SCR urea system. With P2220 the cell current is lower than the expected range. The exact definition can vary by manufacturer, so confirm it in service information for your vehicle.

Symptoms

  • Check engine light on
  • False SCR or catalyst efficiency codes
  • AdBlue/DEF system warning on the dash
  • Possible reduced power
  • Higher NOx emissions
  • Possible no-restart after a countdown

Possible causes

  1. Aged or worn NOx sensor
  2. Contamination on the sensing element
  3. Exhaust leak ahead of the sensor
  4. Wiring shorted to positive
  5. Corroded or damaged connector or harness
  6. Failed sensor or its control module

How to diagnose

  1. Read all codes and freeze frame, and compare with other SCR and NOx codes
  2. Inspect the sensor, connector and harness for damage, moisture, corrosion and chafing
  3. Check the exhaust for leaks upstream of the sensor
  4. Test sensor power, ground and signal circuits against the wiring diagram
  5. Check for a short to battery voltage
  6. Watch NOx sensor live data at idle and during warm-up on a scan tool
  7. Check DEF quality and level and SCR system operation
  8. If wiring is good, replace the sensor and perform any required adaptation

Common fixes

  • Replace the NOx sensor
  • Repair or replace the wiring and connector
  • Fix the exhaust leak ahead of the sensor
  • Correct whatever is contaminating the sensor (SCR or engine faults)
  • Clear codes and verify the repair

Questions and answers

What does P2220 mean?

The ECU detected NOx sensor cell current below the expected range on bank 1. The usual culprits are the sensor itself, its wiring, or an exhaust leak ahead of it.

Can I drive with P2220?

For a short time, yes, but the SCR system isn't controlled accurately, and the vehicle may limit power or refuse to restart after a warning. Get it diagnosed soon.

Should I replace the NOx sensor right away?

No. Check the connector, harness, exhaust leaks and sensor supply first, since the sensor is expensive and wiring is often at fault.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.