P23AB code meaning
NOx Sensor Processor Performance (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23AB means
A NOx sensor is a smart part: the probe in the exhaust is wired to a small control unit with its own processor, which runs the heater, evaluates the cell currents and reports over CAN. P23AB means that this electronics in sensor 3 of bank 1 – usually the one behind a second SCR catalyst – reports an internal error or fails its self-checks. No manufacturer documents P23AB publicly. Ford's 2023 diesel OBD summary shows what such checks contain for its front sensor: RAM failure and ROM or EEPROM checksum errors, reported there under P2200. CARB requires NOx sensors to be monitored for faults that make them unusable for the SCR checks. P06EA and P06EB are the processor codes of sensors 1 and 2. Repair normally means a new sensor.
P23AB at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P23AB
- Check engine light on
- Sensor 3 values missing or frozen in live data
- SCR or emissions warning on the display
Common causes of P23AB
- Most likelyInternal electronics of the sensor 3 control unit defective
- PossibleSupply voltage dips or poor ground resetting the sensor electronics
- Less likelySensor control unit damaged by heat or water ingress
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor b1s3
What each part of P23AB means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| AB | The exact fault in that area. |
What to do next
- Note P23AB and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P23AB
What does P23AB mean?
P23AB means "NOx Sensor Processor Performance (Bank 1 Sensor 3)". A NOx sensor is a smart part: the probe in the exhaust is wired to a small control unit with its own processor, which runs the heater, evaluates the cell currents and reports over CAN. It is a generic code, so it means the same on every make.
Is it safe to drive with P23AB?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P23AB fail an emissions test?
Yes, it can. P23AB is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P23AB to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P23AB clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.