P23BANOx Sensor Heater Sense Circuit Intermittent (Bank 1 Sensor 3)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- With P23BA, the heater feedback signal from the third NOx sensor of bank 1 keeps vanishing or leaping for a moment and then recovers, rather than staying broken. P23BA itself is not described in any public manufacturer document. GM's 2025 table checks this sensor only for the lasting faults P23B4, P23B8 and P23B9, while remarking that a Continental Gen 3.5 probe only passes an electrical fault on after debouncing it for 1.5 s, so very brief dropouts may never reach the engine module at all. CARB asks for continuous monitoring of exhaust gas sensor heater circuits. Smart sensors send their heater circuit status over CAN, which is where an unstable state becomes visible. Loose terminals, a cracked lead near the rear of the exhaust and moisture drawn into the plug as it cools are the usual suspects; the MIL may come and go.
- What you may notice
- Check engine light that comes and goes
- Sensor 3 briefly leaves its ready state
- Fault often cannot be reproduced in the workshop
- Likely causes
- LikelyTerminal in the sensor 3 connector with weak contact pressure
- PossibleSense lead cracked by vibration or heat and opening only at times
- PossibleMoisture entering the plug through a damaged seal
- 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: €20 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.