Emissions

P2224 — NOx Sensor Performance, Bank 2 Sensor 1

Severity: medium Drive with care, to a shop

What P2224 means

The engine control unit compares the signal from the bank 2 nitrogen oxide (NOx) sensor, located ahead of the SCR catalyst, with what it expects based on engine operation. If the reading is implausible or responds incorrectly, P2224 is stored. The exact code definition can vary by manufacturer, so confirm it with a scan tool and vehicle service data. The NOx sensor is used to control diesel exhaust fluid (DEF) dosing and to monitor emissions system efficiency.

Symptoms

  • Check engine light or an SCR system warning
  • Message about an emissions system fault or DEF quality
  • Reduced engine power
  • Possibly higher fuel or DEF consumption
  • Related codes such as P20EE may also be stored
  • Failed emissions inspection

Possible causes

  1. Failed or contaminated bank 2 NOx sensor
  2. Degraded SCR catalyst
  3. DEF not injecting or dosing properly
  4. Poor quality or diluted DEF
  5. Wiring short to positive, open circuit or corroded connector at the sensor
  6. Exhaust leak near the sensor
  7. Faulty NOx sensor control module or ECU (rare)

How to diagnose

  1. Read all codes and freeze frame data, noting P20EE and any other SCR codes
  2. Inspect the sensor, connector and harness for chafing, moisture and corrosion
  3. Check DEF level and quality, and replace it if in doubt
  4. Look for exhaust leaks upstream of or near the sensor
  5. View live NOx sensor data on a warm engine and compare it with the other bank
  6. Check sensor power, ground and CAN communication
  7. Test the DEF injector, pump and system pressure
  8. Evaluate SCR catalyst efficiency using the manufacturer's procedure

Common fixes

  • Replace the bank 2 NOx sensor
  • Repair the sensor wiring or connector
  • Replace the DEF and flush the delivery system
  • Clean or replace the DEF injector, pump or dosing module
  • Replace the SCR catalyst if it has lost efficiency
  • Repair exhaust leaks

Questions and answers

Can I drive with a P2224 code?

For a short time, yes, but the vehicle may limit power and later block engine restarts. Get it diagnosed soon.

Does P2224 always mean a bad NOx sensor?

No. Wiring, bad DEF, an exhaust leak or an SCR problem can cause it too. Check those first, since the sensor is expensive.

Will the code clear on its own?

If the cause was temporary, the light may go out after several passing monitor cycles. If the fault is still present, the code will come back.

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.