Powertrain Controls - ECM/PCM

Diagnostic Chart:

Circuit Schematic:

BYPASS CIRCUIT - OPEN OR SHORTED
The PCM/EC enables the Ignition Control (IC) control circuit mode by switching the bypass line high. When the bypass line is low the Electronic Ignition (EI) module controls secondary coil firing. To enable IC control circuit, the PCM/EC applies five volts on the bypass line (at approximately 400 rpm) indicating IC control circuit mode to the EI module. In IC control circuit mode the El module uses the IC control circuit signal from the PCM/EC to fire the secondary coils. The PCM/EC has internal feedback to monitor the state of the bypass line.

DTC PARAMETERS

DTC 42 will set if:
^ The bypass line is open.
^ The bypass line is grounded.
^ The bypass line is shorted to voltage.

DIAGNOSTIC AIDS
When attempting to diagnose an intermittent problem use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.


Intermittents or opens suspected to be at the connector can be detected by using Diagnostic Service Probe. Voltage can be read on wires without disconnecting any connectors.

Check the tightness of the female terminal grip with a spare male terminal.

If using the Saturn Portable Diagnostic (Scan) (PDT) Tool at the end of the General Information table it will display a 42A, 42B, or 42C.

^ 42A - Bypass line grounded
^ 42B - Bypass line open
^ 42C - Bypass line shorted to voltage

[1] Select Malfunction History from Scan tool Engine Control (EC) menu.