By-Pass Mode

During cranking, or whenever ECM fails, the C(3)I system goes into by-pass mode. In by-pass mode, timing is controlled by ignition module and is preset at 10° BTDC.

At about 400 RPM, ECM applies 5 volts to terminal "B" to switch timing control from ignition module to ECM. An open or grounded by-pass circuit will set a Trouble Code 42.