The engine U1223 Code is important thing and it needs to solve the car engine problem. The automobile meaning of the engine code is easy to find from online. The automobile meaning of the car engine code is U for Network Code Problem is climate control system, lighting, airbags, etc. 1 for MFG – Manufacturer Specific. 2 for BBV Sensor Circuit Low Voltage. 2 for BBV Sensor Circuit Low Voltage and 3 for Transmission. The automobile meaning of the code is not used for fixing the car engine You should be careful if you want to fix the car engine .