OBD-II code · Powertrain (generic, extended)
P23AB NOx Sensor Processor Performance Bank 1 Sensor 3
An internal self-test in the control module reports a fault in its processing of the "NOx sensor processing, bank 1 sensor 3" value. The module computes and cross-checks this value redundantly inside its own processor; when the results disagree, the code sets. It points to a hardware or software fault inside the module itself, not to a defect of the external sensor. Causes are an internal processor or memory fault, corrupted control-module software, or low or disturbed module supply voltage.
Is it safe to drive with P23AB?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyInternal software anomaly
- Less likelyModule software outdated, reflash may resolve
- Less likelySupply voltage outside specification
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)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 2–8 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Sensor B1s3
Related codes
- P06EANOx Sensor Processor Performance Bank 1 Sensor 1
- P06EBNOx Sensor Processor Performance Bank 1 Sensor 2
- P23A8Exhaust Heat Exchanger Bypass Valve B Position Sensor Stop Performance
- P23A9Communication Fault Forced Engine Shutdown
- P23AATurbocharger Bypass Valve A Stuck
- P23ACNOx Sensor Circuit Bank 1 Sensor 3
- P23ADNOx Sensor Circuit Range or Performance Bank 1 Sensor 3
- P23AENOx Sensor Circuit Low Bank 1 Sensor 3
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.