P2223: NOx Sensor Heater Sense Circuit Low (Bank 2)

What it means

NOx Sensor Heater Sense Circuit Low (Bank 2): the signal voltage is below the expected range. The NOx sensor heater brings the sensor to operating temperature; a fault delays accurate NOx readings used for SCR control.

At a glance

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

How it works

The Bank 2 NOx sensor heater warms the sensor so it can measure exhaust nitrogen oxides accurately for emissions control. The control module monitors the heater’s sense signal and sets P2223 when that signal falls below its expected range, which can delay reliable NOx readings and SCR control.

Common causes

Most likely first.

1. Short to ground
2. Connector pins corroded - high contact resistance
3. Harness chafing through insulation

Symptoms

• Check engine light or NOx warning on
• AdBlue/DEF level or quality warning
• Possible no-start countdown after ignore period
• Failed emissions inspection (NOx)

How to diagnose it

1. Use a scan tool to record freeze-frame data and check Bank 2 NOx and heater-related readings for clues about when the low signal occurs.
2. Inspect the Bank 2 NOx sensor connector and nearby harness for corrosion, loose pins, or insulation rubbed through to ground.
3. With the circuit identified from vehicle wiring information, check whether the heater sense wire is shorted to ground.
4. Check connector pin fit and continuity through the Bank 2 heater sense circuit, accounting for corrosion that can raise contact resistance.
5. If the wiring and connections pass, test the Bank 2 NOx sensor heater and its sense output using the manufacturer's diagnostic procedure.

Common fixes

• Clean and secure corroded or loose Bank 2 NOx sensor connector pins.
• Repair chafed Bank 2 heater sense wiring and insulate it from ground contact.
• Replace a damaged connector or terminal that cannot maintain reliable contact.
• Replace the Bank 2 NOx sensor assembly if its heater sense circuit fails testing.

Can I keep driving?

You can usually drive cautiously if the engine runs normally, but arrange diagnosis soon because emissions readings and SCR control may be unreliable. If an AdBlue/DEF warning or no-start countdown appears, follow the vehicle's warning instructions; ignoring it can eventually prevent restarting.