P22A9NOx Sensor Heater Sense Circuit High (Bank 1 Sensor 2)
- 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
- P22A9 is the high-side twin of P22A8: the heater sense line of the rear NOx sensor on bank 1 has a short to supply voltage. The module then reads an element resistance that is far off and loses its temperature feedback, so it cannot hold the probe at working temperature. GM's 3.0L LZ0 looks for a battery short at the HTemp pin once dew point is reached and supply exceeds 9.9 V, 80 failures in 160 samples, Type B after two trips; the 2017 small diesels need 20 failures in 40 samples. In both cases the Continental sensor itself confirms an electrical fault before reporting it. No manufacturer bulletin mentions P22A9. A short often sits where the probe lead runs close to other powered wiring or where a connector has taken in water. P22A6 is the open circuit, P22A8 the ground short, P2211 the front sensor.
- What you may notice
- Malfunction indicator lamp on after two trips
- Outlet NOx sensor not ready
- SCR warning on the display
- Likely causes
- LikelyHeater sense conductor shorted to supply inside the probe
- PossibleProbe lead touching another powered conductor
- RareWater bridging pins in the probe 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: €150 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.