Something I found interesting while surfing my GM SI:

"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 22°C (40°F) from the start-up temperature. The engine coolant must also achieve a minimum temperature of 71°C (160°F). The PCM counts the number of warm-up cycles in order to clear the malfunction indicator lamp (MIL). The PCM will clear the DTCs when 40 consecutive warm-up cycles occur without a malfunction."

I'll be posting more tidbits as I find them.

I liked the part where the PCM (or maybe it was a different module) can remember up to _three_ airbag deployment events, or in other words it can tell a code scanner, "Yeah! My owner'* gotten me into _three_ major accidents so far!"