What does this code mean?
The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
U12A4LOST COMMUNICATION WITH AMMONIA SENSOR Improvements To Prevent Or Reduce Unnecessary Malfunction Indicator Lamp (Mil) Illumination ForU12A4Lost Communication With Ammonia SensorManufacturer communications
3Original wording in English
RAM
Reported code forms U12A4
Flash: 6.7L Diagnostic and System Improvements This bulletin involves selectively erasing and reprogramming the Engine Control Module (ECM) with new software. Several software improvements are available for vehicles…
RAM
Reported code forms U12A4
Flash: 6.7L Diagnostic and System Improvements This bulletin involves selectively erasing and reprogramming the Engine Control Module (ECM) with new software. Several software improvements are available for vehicles…
RAM
Reported code forms U12A4
Flash: 6.7L Diagnostic and System Improvements This bulletin involves selectively erasing and reprogramming the Engine Control Module (ECM) with new software. Several software improvements are available for vehicles…
Check vehicle applicability
3A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.