The automobile dictionary meaning of the car engine P1801 Code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 for MFG – Manufacturer Specific. 8 for Ignition System Or Misfire. 0 for IC Circuit High Voltage. 1 for TFP Valve Position Switch-Drive Without Drive Ratio. This meaning of the code may not useful for solving the car engine. That is why, you should depend on the real meaning what is related with the car engine and it is found from the car manufacturer. Once the car engine is ok, you should take the car for a test drive and it is necessary.