42 Bypass Circuit - Open or Shorted
The PCM/EC enables the EST mode by switching the bypass line high. When the bypass line is low the DIS module controls secondary coil firing. To enable EST the PCM/EC applies 5 volts on the bypass line (at approximately 400 RPM) indicating EST Mode to the DIS module. In EST mode the DIS module uses the EST signal from the PCM/EC to fire the secondary coils. The PCM/EC has internal feedback to monitor the state of the bypass line.
Code 42 will set if:
- The bypass line is open.
- The bypass line is grounded.
- The bypass line is shorted to voltage.
- 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.
- Refer to DIS in the Ignition section.
If using the SATURN PDT, at the end of the General Information table it will display a 42A, 42B, or 42C. See: Scan Tool Testing
- 42A - Bypass line grounded.
- 42B - Bypass line open.
- 42C - Bypass line shorted to voltage.