The engine U1123 Code is very important thing and this engine code has general and real meaning. You also find the automobile meaning of the code for fixing the car engine problem. The automobile meaning of the code is U for Network Code Problem is climate control system, lighting, airbags, etc. 1 for MFG – Manufacturer Specific. 1 for Transmission. 2 for Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and 3 for Transmission Control Module Reprogrammable Memory. This automobile dictionary meaning is found online but this code meaning does not provide real information about your car engine problem. Finally, you should check the car engine by a test drive.