What it means
The resistance of the NOx sensor heater on bank 1 sensor 3 is outside the calibrated band - aged element or contact resistance increased.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The heater element inside the Bank 1 Sensor 3 NOx sensor warms the sensing unit so it can work under the required exhaust conditions. P23BB sets when the measured heater resistance falls outside the module's calibrated range, which may point to a worn element or resistance in its connections.
Common causes
Most likely first.
- NOx sensor heater element worn or damaged
- High resistance at a connector or in the heater wiring
- Poor sensor ground or electrical connection
- Fault within the NOx sensor
Symptoms
- Check engine light
- Possible NOx or aftertreatment warning
- Increased NOx emissions or failed emissions test
How to diagnose it
- Use a scan tool to record freeze-frame data and check for other Bank 1 Sensor 3 heater or supply faults before testing resistance.
- Inspect the NOx sensor connector, heater terminals, wiring, and ground path for corrosion, heat damage, looseness, or chafing.
- With the circuit and sensor isolated as the manufacturer specifies, measure heater resistance and compare it with the manufacturer's specification.
- Check wiring and connector resistance and the sensor ground path to locate excess resistance outside the heater element.
- If wiring and ground are sound but heater resistance is out of range, confirm sensor failure with the manufacturer's diagnostic procedure.
Common fixes
- Clean or repair corroded or loose heater connector terminals.
- Repair high-resistance or damaged Bank 1 Sensor 3 heater wiring or ground connections.
- Secure and protect wiring damaged by exhaust heat or vibration.
- Replace the Bank 1 Sensor 3 NOx sensor if its heater element fails the resistance test.
- Repair the heater circuit if testing identifies a control-side fault.
Can I keep driving?
The code does not usually mean the vehicle will stop immediately, but the NOx sensor may not operate correctly and emissions can rise. Drive cautiously and arrange repair, especially if an aftertreatment warning appears or the vehicle is due for an emissions test.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.