The general meaning of the P20AA Code is not helpful. The manufacturer of the automobile sets a meaning for the car engine and that is the real meaning. Do not drive the car with the engine problem and do not use the general information for solving the car engine problem. The general meaning of the code is P for Powertrain Code – Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 0 for Transmission. A for BBV Sensor Circuit Low Voltage and A for TFP Valve Position Switch-Drive Without Drive Ratio. Do not drive the car with faulty engine.