What it means
Same as P23C0 with a measurable delay before the sensor begins to track falling levels - the start of the response is delayed, not just the slope.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The NOx sensor at Bank 1 Sensor 3 tracks nitrogen oxides in the exhaust for aftertreatment monitoring. This code sets when its reading takes too long to begin falling after exhaust NOx levels drop, indicating a delayed high-to-low response rather than simply an inaccurate steady reading.
Common causes
Most likely first.
- NOx sensor element aging or degradation
- Sensor contamination or exhaust deposits
- Poor sensor connector contact
- Fault in the sensor signal wiring
Symptoms
- Check engine light
- Possible NOx or aftertreatment warning
- Increased NOx emissions or failed emissions test
How to diagnose it
- Check freeze-frame data and related codes to identify the conditions when the Bank 1 Sensor 3 response delay was detected.
- Graph Bank 1 Sensor 3 NOx live data during changing engine or aftertreatment conditions and compare the timing with other available exhaust readings.
- Inspect the Bank 1 Sensor 3 connector and wiring for loose contact, corrosion, heat damage, or chafing that could delay the signal.
- Look for exhaust leaks or deposits around the sensor that could affect the gas reaching its sensing element.
- Test the sensor power, ground, and signal wiring against the manufacturer's specification, including connector contact when the harness is moved.
- If wiring and exhaust checks pass, use the manufacturer's response test to determine whether the Bank 1 Sensor 3 element has aged or degraded.
Common fixes
- Repair a loose, corroded, or damaged Bank 1 Sensor 3 connector or harness.
- Repair any exhaust leak or contamination source found near the sensor.
- Replace the Bank 1 Sensor 3 NOx sensor if it fails the response test and its circuits are sound.
- Clear the code and confirm the sensor tracks falling NOx readings without delay.
Can I keep driving?
If the engine runs normally, a short cautious drive is generally possible, but the delayed reading can impair emissions monitoring and lead to a failed emissions test. Limit unnecessary driving and investigate promptly if an aftertreatment warning appears.
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.