This engine P2681 Code contains information about the car engine problem. This engine code shows that the PCM has noticed an fault in the engine coolant bypass valve control circuit. If this engine code is kept and a service of car engine soon lamp is yet to be illumined it may be revealed as incomplete. Unlike the most other PCM engine codes, the most probable reason of this code being deposited is a faulty driver in the PCM or a poor electrical joining. The car engine should be diagnosis properly to know the exact cause of the car engine problem.