P23B5NOx Sensor Heater Sense 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
- P23B5 says the heater feedback from NOx sensor 3 (bank 1) is present but implausible: the element does not reach or hold the resistance that matches its target temperature. GM's 2025 diesel table 25OBDG04B compares the raw heater resistance of the post-second-catalyst sensor with its target and fails it outside a relative band of 0.06, after waiting 200 s from supply in range and from dew point; 125 of 250 samples, Type A. Ford lists P23B5 for 2023 Super Duty trucks with the 6.7L diesel together with P2209, P22A7 and NOx sensor communication codes (SSM 51750, 51791): harness 14406 chafes on the right-hand EGR cooler near connector C146, so fuse F18 (20 A) is checked first. P23B4 is the open sense line.
- What you may notice
- Check engine light after one trip
- Several NOx sensor and communication codes at once
- SCR warning, sensor 3 not ready
- Likely causes
- LikelyNOx sensor harness chafing on a hot component such as the EGR cooler (Ford 2023 6.7L)
- PossibleAged heater element whose resistance no longer matches the target
- PossibleBlown fuse in the NOx sensor supply after a short
- RareHigh contact resistance in the heater connector
- 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 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.