P224B: NOx Sensor Heater Resistance (Bank 1 Sensor 2)

What it means

The measured heater element resistance of the NOx sensor on bank 1 sensor 2 is outside the calibrated range. Used as a sensor-element health check.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Bank 1 Sensor 2 is the downstream NOx sensor, and its heater brings the sensing element to operating temperature so the emissions system can measure nitrogen oxides. The control module checks the heater element’s resistance as a health check; this code sets when that resistance is outside the calibrated range.

Common causes

Most likely first.

1. NOx sensor heater element worn or damaged
2. Poor connector contact or corroded terminals
3. Open or short in heater wiring

Symptoms

• Check-engine light or NOx warning may illuminate
• Possible emissions warning

How to diagnose it

1. Read freeze-frame data and related NOx or heater codes to see the conditions when the resistance fault was detected.
2. Inspect the Bank 1 Sensor 2 connector and nearby harness for corrosion, loose terminals, heat damage, or chafing.
3. Check the sensor’s heater circuit wiring for an open or short, following the vehicle wiring diagram.
4. With the sensor disconnected as specified by the manufacturer, measure the heater element resistance and compare it with the manufacturer’s specification.
5. If wiring and connections are sound but the resistance remains out of range, test or replace the Bank 1 Sensor 2 NOx sensor as indicated by the manufacturer’s procedure.

Common fixes

• Clean and secure corroded or loose Bank 1 Sensor 2 connector terminals.
• Repair an open or shorted heater wire in the sensor harness.
• Replace the Bank 1 Sensor 2 NOx sensor if its heater resistance is out of specification.

Can I keep driving?

The vehicle may remain drivable, but the NOx or emissions warning can stay on and emissions control may be impaired. Avoid ignoring the fault if an emissions test is due.