P23B7NOx Sensor Heater Control Circuit Range/Performance (Bank 1 Sensor 3)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light on
- Sensor 3 takes long to become ready or drops out of its active state
- SCR efficiency monitor not completing
- Likely causes
- LikelyAged heater element that needs far more or less power than expected
- PossibleHigh resistance in heater supply or ground contacts
- RareSensor supply voltage at the lower limit, so the heater cannot keep up
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.