Ignition Mode

The scan tool displays BYPASS or IC. This indicates the commanded state of the Bypass signal output from the PCM. When BYPASS is displayed, the ignition control module is controlling the spark advance at a fixed 10° BTDC (Bypass mode). IC displayed indicates that the PCM has requested control of the spark advance (IC mode). 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 conditions are appropriate for PCM control of spark timing (IC mode). If the PCM does not apply 5 volts to the bypass circuit, or if the ignition control module does not receive the voltage, the module controls spark timing.