The car engine P2123 Code helps for solving the car engine problem. The general meaning of the car engine code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 1 for Transmission. 2 for Air Conditioning Clutch Feedback Circuit High Voltage and 3 for Transmission Control Module Reprogrammable Memory. There are now 2 main kinds of cylinder diffusion used nowadays, depending on the kind of engine. The engine P2123 code for the pushrod design which uses solenoids to change the oil compression delivered to the lifters. In their collapsed state, the lifters are powerless to upraise their companion pushrods underneath the valve rocker arms.