By-Pass Signal

When engine speed is less than 400 RPM, the ignition module controls spark using a predetermined interval based on engine speed alone. When engine speed is greater than 400 RPM, the ECM applies 5 volts to the by-pass circuit to switch spark timing control from the DIS module to the ECM. On open or grounded by-pass circuit will cause the engine control system to operate in an ignition timing back-up mode. A code 42 will be set.