Warm-Up Cycle
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
The PCM uses warm-up cycles to run some diagnostics and to clear any Diagnostic Trouble Codes (DTCs). A warm-up cycle occurs when the engine coolant temperature increases 40°F (22°C) from the start-up temperature. The engine coolant must also achieve a minimum temperature of 160°F (71°C). The PCM counts the number of warm-up cycles to clear the Malfunction Indicator Light (MIL). The PCM will clear the DTCs when 40 consecutive warm-up cycles occur without a malfunction.