The general meaning of the car engine P3403 Code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 3 for SAE – Generic. 4 for Transmission. 0 for IC Circuit High Voltage and 3 for Transmission Control Module Reprogrammable Memory. Here, it seems that the powertrain is faulty and you need to fix the problem as soon as possible. Although, this car engine’s powertrain problem is not so serious problem but you should not take any risk. The small problem can be a cause of the serious problem of the car engine and you should not ignore any problem from the car engine.