P22A3 code meaning
NOx Sensor Heater Control Circuit/Open (Bank 1 Sensor 2)
Powertrain system Generic code P22xx codes Check engine light
What P22A3 means
The ceramic element of a NOx sensor measures only after its built-in heater has brought it to several hundred degrees. P22A3 reports a break on the heater control side of the rear sensor on bank 1, behind the SCR catalyst. GM's 6.6L LML sets it when the sensor reports an open heater over CAN longer than 10 s, Type A. On the 3.0L LZ0 the heater control pin is tested for a missing load (80 failures in 160 samples), on the 2017 small diesels the H+ supply pin of the Gen 3.0 sensor; both Type A, so the MIL comes on after one trip. Volvo and Mack read P22A3-13 as a probable outlet sensor failure, and GM bulletin 24-NA-094 lists the code for an LZ0 software update. P22A4 and P22A5 are shorts, P22A6 the heater sense line, P2205 the front sensor.
P22A3 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 repairWhen cleared with a scanner
Symptoms of P22A3
- Malfunction indicator lamp on after one trip
- Outlet NOx sensor never reports ready
- SCR warning on the display
Common causes of P22A3
- Most likelyHeater element in the outlet NOx probe burnt through
- PossibleBroken conductor between probe and sensor module
- 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 P22A3 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). |
| A3 | The exact fault in that area. |
What to do next
- Note P22A3 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 P22A3
What does P22A3 mean?
P22A3 means "NOx Sensor Heater Control Circuit/Open (Bank 1 Sensor 2)". The ceramic element of a NOx sensor measures only after its built-in heater has brought it to several hundred degrees. It is a generic code, so it means the same on every make.
Is it safe to drive with P22A3?
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 P22A3 fail an emissions test?
Yes, it can. P22A3 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 P22A3 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 P22A3 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.