P22A8NOx Sensor Heater Sense Circuit Low (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
- P22A8 means the heater sense line of the rear NOx sensor on bank 1 is shorted to ground; the sensor module uses that line to read the element temperature via its resistance. With that line pulled to ground, the module sees a temperature value it cannot trust and cannot regulate the heater properly. GM documents the test on the 3.0L LZ0: ground short at the HTemp pin, judged with dew point reached and sensor supply above 9.9 V, 80 failures in 160 samples, Type B after two trips; the Continental Gen 3.5 sensor debounces such faults internally for 1.5 s. GM's 2017 small diesels use the same check with 20 failures in 40 samples. No public bulletin names this code. P22A6 is the open circuit, P22A9 the short to voltage, P2210 the front sensor.
- What you may notice
- Malfunction indicator lamp on after two trips
- Outlet NOx sensor not ready
- SCR efficiency check does not run
- Likely causes
- LikelyHeater sense conductor shorted to ground inside the probe
- PossibleProbe lead insulation damaged against exhaust or body
- 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.