U02A4: The ammonia sensor is not answering on the car network
The ammonia sensor is not answering on the car network. It is usually that control unit, its power supply or the network wiring.
| Code | U02A4 |
|---|---|
| System | Communication network |
| Group | U02xx, Lost communication with control units |
| Type | Generic: it means the same on every make |
How to read and clear U02A4 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see U02A4 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- U029F The evaporative emission system leak detection control unit is not answering on
- U02A0 The high voltage battery interface control unit D is sending data that cannot
- U02A1 The NOx sensor C is not answering on the car network
- U02A2 The AdBlue quality module is not answering on the car network
- U02A5 The AdBlue heater control unit is not answering on the car network
- U02A7 The engine 1 sound control is not answering on the car network
- U02A8 The engine 2 sound control is not answering on the car network
- U02AB The vehicle thermal management control unit is not answering on the car network
What does code U02A4 mean?
The ammonia sensor is not answering on the car network. It is usually that control unit, its power supply or the network wiring.
How do you clear U02A4?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, U02A4 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
