The Power Train Control Module (PCM) or Engine Control Module (ECM) controls all aspects of the operation of the engine, including the electrical system.
When the vehicle starts, the ECM or PCM performs a self-test of all the components of the engine and the rest of the vehicle, in order to verify the proper functioning of all these. If after that self-verification, as a result there is a processor failure in the vehicle’s computer, the DTC code P0606 OBD2 is established.