The automobile dictionary meaning of the car engine P1851 Code provides some information what you may use but you must look for the actual meaning of the code what is found from the car manufacturer. The general meaning of the 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. 5 for TP Sensor Learn Not Complete and 1 for TFP Valve Position Switch-Drive Without Drive Ratio. The real meaning of the car engine code may not similar to the general meaning of the car engine code.