Ignition Mode

Scan tool displays BYPASS or IC. Indicates the commanded state of the Bypass signal output from the PCM. When BYPASS is displayed, the Ignition Control (IC) module is controlling the spark advance at a fixed 10 degrees Before Top Dead Center (BTDC). IC displayed indicates that the PCM has requested control of the spark advance. The ignition control module determines the correct operating mode based on the level of voltage that the PCM applies to the ignition control module bypass circuit. The PCM provides 5 volts to the ignition control module bypass circuit when the conditions are appropriate for PCM control of the spark timing. This represents IC mode. If the PCM does not apply 5 volts to the bypass circuit, or if the ignition control module does not receive it, the module will control spark timing. This represents BYPASS mode.