The engine P1786 Code is a helping code and it is necessary to solve the car engine quick. The powertrain is the defective here and it needs to fix for solving the car engine. For solving any problem from the car engine, you should depend on the expert automobile engine who knows the process of solving the car engine. The automobile dictionary meaning can be used if it is necessary. The automobile dictionary meaning is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 for MFG – Manufacturer Specific. 7 for Auxiliary Emission Controls. 8 for Exhaust Gas Recirculation System Valve 1 and 6 for Cruise Control System – Vehicle Accel Too High.