Abstract: An engine ignition control circuit includes a crank angle sensor and two reference position sensors. The engine ignition control circuit also includes an ignition timing control unit generating primary ignition signals and a replacement ignition signal generator device. The control circuit further includes a crank angle monitoring circuit which detects the failure of the crank angle sensor and generates a malfunction signal. The malfunction signal controls a data selector which outputs either the primary ignition signals or the replacement ignition signals to drivers and ignition coils for the engine.