P23B7 code meaning
NOx Sensor Heater Control Circuit Range/Performance (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23B7 means
P23B7 is set when the heater drive of NOx sensor 3 on bank 1 looks electrically sound but does not behave as the control strategy expects, for instance a heater duty cycle far from what the element should need to reach operating temperature. No manufacturer documents P23B7 publicly; GM's 2025 table covers sensor 3 only with the plain heater circuit codes P23B1-P23B3 and the resistance check P23B5. Ford's 2023 diesel summary shows how the front-sensor counterpart P220E is judged: apart from open and shorted heaters a heater whose duty cycle misses the expected figure by over 20 percent is also treated as faulty. CARB requires sensor heater performance to stay within the supplier's limits. If the element never gets hot enough, sensor 3 stays inactive; P220F is the sensor 2 version.
P23B7 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P23B7
- Check engine light on
- Sensor 3 takes long to become ready or drops out of its active state
- SCR efficiency monitor not completing
Common causes of P23B7
- Most likelyAged heater element that needs far more or less power than expected
- PossibleHigh resistance in heater supply or ground contacts
- Less likelySensor supply voltage at the lower limit, so the heater cannot keep up
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 P23B7 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. |
| B7 | The exact fault in that area. |
What to do next
- Note P23B7 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 P23B7
What does P23B7 mean?
P23B7 means "NOx Sensor Heater Control Circuit Range/Performance (Bank 1 Sensor 3)". P23B7 is set when the heater drive of NOx sensor 3 on bank 1 looks electrically sound but does not behave as the control strategy expects, for instance a heater duty cycle far from what the element should need to reach operating temperature. It is a generic code, so it means the same on every make.
Is it safe to drive with P23B7?
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 P23B7 fail an emissions test?
Yes, it can. P23B7 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 P23B7 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P23B7 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.