Th engine U1023 Code is not everything if you do not get the genuine meaning of the code. The genuine meaning of the code is actual information and it is found from the manufacturer of the car. The general meaning of the code is not helpful and that is U for Network Code Problem is climate control system, lighting, airbags, etc. 1 for MFG – Manufacturer Specific. 0 for Fuel And Air Metering. 2 for Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and 3 for Transmission Control Module Reprogrammable Memory. The U1023 engine code appears a kind of network problem what is easy to fix.