DTCs Current and History

The BCM has the ability to store DTCs as current or history codes. When the BCM stores a DTC, the BCM may send a massage on the serial data line to the Instrument Panel Cluster (IPC) to display a warning message indicating a DTC is current. For most DTCs, the BCM will NOT display a warning message. Current DTCs can be stored in two classifications: latched, and unlatched. Latched current codes are those indicating a malfunction is present, but will still remain current even after the malfunction no longer exists. These current codes will continue to display as current until the ignition is cycled OFF then ON. Unlatched codes will clear as soon as the malfunction is no longer present and does not require the ignition to be cycled. History DTCs are those indicating that the BCM previously detected a malfunction which later disappeared. The reason could be either that the malfunction is intermittent, only happening occasionally, or that the system for which the DTC is set is not currently being operated. History DTCs are intermittent malfunctions and must be diagnosed differently than current DTCs. Refer to Intermittents and Poor Connections. Intermittents and Poor Connections