P22A4 code meaning
NOx Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
Powertrain system Generic code P22xx codes Check engine light
What P22A4 means
P22A4 means the heater control line of the rear NOx sensor on bank 1 has a short to ground, so the sensor module can no longer drive the heater as commanded. GM documents it on the 3.0L LZ0 as a ground short on the heater control pin, judged once dew point is reached and sensor supply exceeds 9.9 V, 80 failures in 160 samples, Type B after two trips. Its 2017 small diesels watch the H+ supply pin of the Gen 3.0 sensor instead, 20 failures in 40 samples. Volvo and Mack count P22A4 among codes that indicate a damaged outlet sensor, and GM bulletin 24-NA-094 adds it to an LZ0 software update for 2024 Silverado and Sierra 1500. Expect the MIL after two trips and no downstream NOx data. P22A3 is the open circuit, P22A5 a short to voltage, P2206 the front sensor.
P22A4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P22A4
- Malfunction indicator lamp on after two trips
- Outlet NOx sensor stays not ready
- SCR warning on the display
Common causes of P22A4
- Most likelyHeater element or probe lead shorted to ground inside the sensor
- PossibleProbe lead insulation chafed against the exhaust or body
- Less likelySoftware anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensorNox sensor heater
What each part of P22A4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 2 | Area: fuel and air metering (injector circuit). |
| A4 | The exact fault in that area. |
What to do next
- Note P22A4 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 P22A4
What does P22A4 mean?
P22A4 means "NOx Sensor Heater Control Circuit Low (Bank 1 Sensor 2)". P22A4 means the heater control line of the rear NOx sensor on bank 1 has a short to ground, so the sensor module can no longer drive the heater as commanded. It is a generic code, so it means the same on every make.
Is it safe to drive with P22A4?
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 P22A4 fail an emissions test?
Yes, it can. P22A4 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 P22A4 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P22A4 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.