Start (Cranking) Signal

The start (cranking) signal from starter relay signals PCM when starter is engaged. When PCM determines starter is engaged, it begins to monitor inputs from crankshaft position sensor and camshaft position sensor.

The PCM uses these signals to determine spark timing and whether the first fuel injection should occur at cylinder No. 4 or 1 (4-cylinder) or cylinder No. 3 or 4 (6-cylinder). Once synchronization has been established, the PCM energizes the proper injector and provides the ignition output needed to start the engine.