P23C0 code meaning
NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23C0 means
With P23C0 the third NOx sensor on bank 1 is too sluggish when NOx falls, for instance when the driver lifts off and the engine goes into fuel cut-off. The module measures how long the reading takes to come down between two levels. No manufacturer documents P23C0 publicly. GM's 2016 diesel table judged the front-sensor counterpart P22FA during a load-to-overrun manoeuvre using a short and a long timer, failing it beyond 4 s on the first or 8 s on the second, Type B. Deposits from condensate, fuel or oil on the sensor element slow the gas exchange and age it faster, as HELLA notes. CARB expects such response-rate losses to be detected. A sensor that lags on the way down keeps reporting NOx that is already gone, which can make the SCR system look less effective than it is. P22FA and P22FD are sensors 1 and 2.
P23C0 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 repairAfter a drive cycle
Symptoms of P23C0
- Check engine light on
- Sensor 3 value stays raised for seconds after lifting off
- Driveability unaffected
Common causes of P23C0
- Most likelyDeposits from condensate, fuel or oil on the sensor element
- PossibleHoles in the protective tube partly blocked by soot or urea crystals
- PossibleSensor aged and no longer able to release its reading quickly
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 P23C0 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. |
| C0 | The exact fault in that area. |
What to do next
- Note P23C0 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 P23C0
What does P23C0 mean?
P23C0 means "NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 3)". With P23C0 the third NOx sensor on bank 1 is too sluggish when NOx falls, for instance when the driver lifts off and the engine goes into fuel cut-off. It is a generic code, so it means the same on every make.
Is it safe to drive with P23C0?
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 P23C0 fail an emissions test?
Yes, it can. P23C0 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 P23C0 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 P23C0 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.