The "usual" difference between a Powertrain Control Module and an Engine Control Module is what they control. The PCM is usually a combined unit with the ECM, TCM, and more inside it. While an ECM may only control the engine.
The Equinox has a PCM. From the factory they are programmed using your VIN number to operate all of the motion related items on the car, engine, transmission, security, ABS, charging system. They are not a plug and play item. None of the modules are any longer. Even the fuel pump requires programming of the module that controls it.
To determine what the problem really is you need to run a series of tests using a factory level scan tool. Then re-flash the PCM with any updates and see if the issue goes away. You may want to call a dealer and have them run your VIN. GM had a problem with 05 and some 06 PCMs acting this way and had a repair. Yours may be covered. If not then you still may be able to have your current PCM updated.
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Tuesday, March 21st, 2017 AT 8:46 PM