41 Ignition Control (IC) Circuit - Open or Shorted

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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.

Code Parameters

Code 41 will set if:

  • The EST circuit is open.
  • The EST circuit is shorted to ground or voltage.

Diagnostic Aids

  • When attempting to diagnose an intermittent problem use the Scan Tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool TC menu.
  • Check the tightness of the female terminal grip with a spare male terminal.
  • The PCM will hold EST low when there are no reference pulses.
  • PCM resistance with no EST output is approximately 14 M ohms.
  • Refer to Ignition section for further information.

If using the SATURN PDT at the end of the General Information table will display a 41A or 41B. See: Scan Tool Testing

  • 41A - EST Circuit open.
  • 41B - EST Circuit shorted to ground or voltage.