Functional Description - Powertrain Control Module (Pcm)

The PCM receives input signals from various sensors that are referred to as PCM inputs. Based on these inputs, the PCM adjusts various engine and vehicle operations including ignition timing.

The PCM provides a common return (ground) circuit for the ignition coils. The PCM controls the operation and firing of each ignition coil through a 5 volt signal circuit. The 5 volt signal circuit turns on a transistor inside the ignition coils to energize the coils. The PCM opens the 5 volt signal circuits individually in sequence allowing the magnetic field built up inside the ignition coils to collapse into the secondary side of the coils and fire the spark plugs.

The PCM can advance or retard the ignition firing sequence based on several inputs to allow the catalytic converters to heat up quickly during a cold start, and to maximize efficiency of the engine operation and tailpipe emissions.