P2BA7

NOx Exceedence - Empty Reagent Tank

Diesel emissions (SCR/DEF) Generic OBD-II High

What it means

P2BA7 is a diesel SCR code meaning NOx emissions have exceeded the limit because the reagent (DEF/AdBlue) tank is empty. To stay emissions-legal the vehicle warns you, then reduces power and may refuse to restart until you refill. The fix is almost always simply topping up diesel exhaust fluid, so act on it before the countdown strands you.

High

Can I keep driving? Limited and time-critical — with the DEF/reagent tank empty the vehicle will warn, then reduce power (derate) and may refuse to restart. Refill diesel exhaust fluid immediately.

Real-world scan data

Seen in

583

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P2BA7 scans

P2201in 64.3% of scans

P2200in 58.5% of scans

P202Din 58.1% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

DEF/AdBlue warning light or message with a distance/restart countdown
Reduced engine power (derate) and capped speed
Vehicle may refuse to restart once the countdown expires
Check-engine light on

Common causes

Most likely first

Diesel exhaust fluid (DEF/AdBlue) reagent tank is emptyLikely
DEF quality poor or diluted (water added, wrong fluid)Common
Faulty DEF level sensor reading emptyCommon
DEF pump, injector, or lines blocked/frozen so reagent is not dosedLess often
NOx sensor or SCR fault causing a false exceedance (less common)Less often

How to diagnose & fix

Work through it in order

Refill the DEF/reagent tank with fresh, correct-spec diesel exhaust fluid first.
Cycle the ignition and allow the system to re-prime and re-check the level; the derate should clear.
If it stays empty after filling, check the DEF level sensor and for leaks or a blocked pickup.
Test the DEF pump/injector dosing and the NOx sensors if the exceedance persists.
Clear the code (or let it self-clear) and confirm normal power returns after a drive cycle.

FAQ

Quick answers

Is it safe to drive with P2BA7?+

Only until you can refill. The system deliberately reduces power and can block a restart to force a DEF refill. Top up the reagent as soon as possible.

Can I just clear P2BA7?+

No. Clearing it does nothing if the tank is empty — refill DEF first. The code and derate lift once the system detects proper reagent.

Read & clear P2BA7 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX