On Cadillac and Saturn models, the PCM contains a feature that allows it to record a snapshot or movie. The feature only works when the vehicle diagnostic tests are off. To activate this feature, press OFF and FRONT DEFROST on the dash controls simultaneously.
The next step is to retrieve the data captured with this feature with a Scan Tool. The data will appear as a DTC Snapshot with the trouble code designation of P0001. Be aware that any previous Customer Snapshot data will be overwritten when another snapshot is initiated.