Ignition/Crank Signal

The PCM monitors initial cranking (RPM) signal to determine when the engine is being started. Moving the ignition switch to the CRANK position sends a 12 volt signal to the PCM Ignition Crank Sense. The PCM verifies that the transmission is in the PARK or NEUTRAL position. The PCM then grounds the control circuit of the START relay. When the START relay is energized it allows voltage to the starter solenoid "S" terminal. The PCM receives three ignition inputs from the ignition switch: ignition 0 signal, ignition 1 signal, and crank signal. The PCM receives the ignition 0 signal with the ignition switch in the CRANK position. The ignition switch sends this signal through the Off/Run/Crank voltage circuit. The PCM uses a Class II ignition mode message and voltage input from separate systems to test the Off/Run/Crank voltage circuit. If the PCM detects an improper input, a related Diagnostic Trouble Code (DTC) will set.