is the pcm part of the drive train
What do you mean by part of it? The PCM is the Power Control Module or the brains/computer of the vehicle. I'd say it's more part of the electrical system of the vehicle.
Basically no. It is part of the emission control system.
The Drive Train is directly responsible for transferring power from the Prime Motivator (the engine) to the wheels. So, the transmission, drive line or drive shaft(s), differential, Transfer case etc.: are all part of the Drive Train. The PCM or Power Train Control Module typically operates the engine - however, in many cases, the PCM also operates the Transmission so, in that respect, it could be considered "part" of the Drive Train but technically, it is not.
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