Everyone that owns a Silverado, specifically a 2004, would you check to see if your check engine light comes on and then goes off after a second or two. Do this without starting the engine and try it a few times. The check engine light is supposed to turn on and then off with the rest of check lights after about two seconds or so. This is self test of all the sensors and electrical. The reason I ask is because sometimes my check engine light does not come on when I turn the key on. But when it does come on (engine not running) it will not turn off when all the other lights have turned off. I`m thinking I may have a PCM problem. But there are no codes in the PCM! Tell me what yours does, please. I`m certain it is supposed to turn on and then off after a couple of secs. every time when you turn the key to run position.