P2BAA
- Powertrain
- Manufacturer-specific
- Emissions
Diagnose soon
Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
NOx Sensor Range/Performance (Bank 1, Sensor 1)
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
The upstream NOx sensor on bank 1 returns values that are not plausible for the current operating point. NOx sensors are slow to warm up, sensitive to soot and water, and are a frequent failure on diesel SCR systems.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Many vehicles show no symptom at all beyond the warning light. The absence of a symptom does not mean the fault is not real.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | NOx sensor element failed | Very common | — |
| 2 | Sensor contaminated with soot or condensate | Common | — |
| 3 | Sensor element aged beyond calibration window | Occasional | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- NOX Sensor Upstream
- NOX Sensor Wiring
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
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