How do you reset a PCM on a 1999 Saturn L series?

To reset the PCM (Powertrain Control Module) on a 1999 Saturn L series, disconnect the negative battery cable and leave it disconnected for about 15 minutes to allow any residual power to drain. This helps clear any stored trouble codes and resets the PCM. After that, reconnect the battery cable, and the PCM will be reset. It's also helpful to drive the car for a short distance to allow the PCM to recalibrate itself.