Circuit Description

Ignition signal and ignition fail-safe signal provide crucial information in control of ignition system timing, injector timing and fail-safe activation. Based on initial timing calculated by crankshaft and camshaft sensor signals, PCM sends an ignition signal to ignition control module (located in ignition coil) and uses it as a reference point to determine ignition dwell.

A circuit within ignition control module controls ignition dwell and spark period by controlling power transistor switch on and off. After spark has occurred, ignition control module sends an ignition fail-safe signal to PCM, confirming an ignition event has taken place. If fail-safe signal is not received by PCM, fail-safe mode is activated and fuel injector operation is ceased to prevent catalytic converter damage. DTC P1300 will set when no ignition fail-safe signal is received by PCM for 2 consecutive ignition cycles during engine operation. When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.