The real meaning of the P040B Code is necessary to solve the car engine problem and if the real meaning is not found, it becomes difficult to solve the car engine problem. You need to know the car manufacturer name and model number of the car. You may read the general meaning and it is P is Powertrain Code – Problem is related engine, transmission and emissions systems. 0 is SAE – Generic. 4 is Fuel And Air Metering. 0 is Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and B for TFP Valve Position Switch-Drive Without Drive Ratio. Do not drive the car until the car engine is fixed.