Electronic Spark Timing

Ignition System Wiring.:

OPERATION
The PCM provides the EST signal. The DIS module uses this signal to fire the ignition coils, this is EST mode (bypass line high). In bypass mode, (bypass line low) the DIS module will ground the EST line and generate an internal signal to fire the ignition coils. The DIS module has the ability to force the bypass line low in the event of missing EST pulses. The PCM monitors the state of the EST line while cranking and running.






EST MODE
EST mode is defined as any time during engine operation that the EST signal is controlling ignition spark timing. The BYPASS line is raised by the PCM. The DIS module shall release the EST line within 5 milliseconds after the BYPASS line is raised. The PCM shall pulse the EST signal with a minimum pulse width of 1.0 millisecond. The falling edge of the EST signal defines the desired timing for the ignition event.