P23BB code meaning
NOx Sensor Heater Resistance (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23BB means
P23BB says the heater element of NOx sensor 3 on bank 1 has a resistance outside its permitted band. Because the resistance of the ceramic heater climbs with temperature, it doubles as the thermometer of the probe, so an aged or cracked element heats poorly and reports a false temperature as well. No manufacturer publishes P23BB. GM runs the same kind of check on the post-second-catalyst sensor in 25OBDG04B but stores P23B5: the raw resistance may differ from its target by no more than 0.06 in relative terms, tested once supply and dew point have been valid for 200 s, 125 of 250 samples, Type A. Under CARB, the heater must be watched against the limits its supplier guarantees. P224A and P224B are the same fault on sensors 1 and 2; the usual remedy is a new sensor.
P23BB 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 P23BB
- Check engine light on
- Sensor 3 slow to become ready after a cold start
- Implausible NOx readings from the rear sensor
Common causes of P23BB
- Most likelyHeater element aged by long service at high exhaust temperature
- PossibleElement cracked by water droplets hitting the hot ceramic
- Less likelyAdded resistance from a corroded heater contact
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor b1s3 heater
What each part of P23BB 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. |
| BB | The exact fault in that area. |
What to do next
- Note P23BB 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 P23BB
What does P23BB mean?
P23BB means "NOx Sensor Heater Resistance (Bank 1 Sensor 3)". P23BB says the heater element of NOx sensor 3 on bank 1 has a resistance outside its permitted band. It is a generic code, so it means the same on every make.
Is it safe to drive with P23BB?
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 P23BB fail an emissions test?
Yes, it can. P23BB 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 P23BB 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 P23BB 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.