•  These appear when a problem is detected in a monitored system. The code for a malfunctioning system is stored in the PCM memory in the first drive cycle. This code is called the pending code. If the PCM determines that the system returned to normal or the problem was mistakenly detected, it deletes the pending code. If the problem is also found in a second drive cycle, the PCM determines that the system has failed, and the DTC is stored.