Without meaning of the car engine code, it is not possible to identify the car engine problem fast. The car engine can be found if the car engine is tested and for this test, you need to take the car to automobile repair center. The car engine P2668 Code is found after the car engine is tested. Now the general meaning of the code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 6 for Vehicle Speed Control And Idle Control System. 6 for Control Module Throttle Actuator Position Performance and 8 for PCM Stack Overrun.