P23B5 code meaning
NOx Sensor Heater Sense Circuit Range/Performance (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23B5 means
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.
P23B5 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P23B5
- Check engine light after one trip
- Several NOx sensor and communication codes at once
- SCR warning, sensor 3 not ready
Common causes of P23B5
- Most 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
- Less likelyHigh contact resistance in the heater connector
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 P23B5 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. |
| B5 | The exact fault in that area. |
What to do next
- Note P23B5 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 P23B5
What does P23B5 mean?
P23B5 means "NOx Sensor Heater Sense Circuit Range/Performance (Bank 1 Sensor 3)". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P23B5?
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 P23B5 fail an emissions test?
Yes, it can. P23B5 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 P23B5 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P23B5 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.