Auto Electronics: engine light flashes, obd2 code scanner, obd2 scanner

Question
okay so i have a 1997 chevy dually 454 vortech engine. trucks bin running great. yesterday i put gas in truck ran a lil sluggish but didnt really notice it. today trucks running like crap. in idle the truck shakes when i exelorate it takes off slow  untill i floor it to get going at a faster pace.when i say floor  it takes off sluggishly so i floor it to getgoing fast. the only thing that conserns me is that my check engine light after about 5 minutes or so starts flashing and wont stop untill i turn the truck off. if you need further info please ask.

Answer
Hello Frank,
 
 The Check engine light is primarily used to alert the operator when there is a malfunction that will adversely increase the vehicles tailpipe or evaporative emissions.  The Check engine light will also alert the operator there is a cylinder miss fire by flashing it once the miss fire counter has recognized which cylinder it is.  This process is different from vehicle to vehicle with some vehicles being notoriously inaccurate with their ability to selectively identify the contributing cylinders and some being increasingly more accurate. GM's are very accurate in their missfire ability.
 There are one of two possibilities happening with your vehicle.  A. There is a cylinder that is miss firing individually because of inadequate fuel or spark requirements such as a bad spark plug or injector or B: there is multiple random cylinders miss firing because of an induced problem such as low fuel pressure, incorrectly calibrated or defective sensor etc,
 The first thing to figure out is what cylinder is missfiring by accessing the PCM and retrieving the related trouble code or codes. This can only be done with an OBD2 code scanner, aftermarket scan tool or my personal preference... a TECH2 dealer scan tool.  The OBD2 scanner will suffice with this type of repair.  It may not give you the amound of missfires or times they happened such as the TECH2 will but it will lead us down the road to diagnosis without spending more than the truck is worth.  You can buy a code scanner at a parts distributor for around 30-40 dollars.  They will scan them for you for free but you will want to have one in your glove box for the price.
 Scan for trouble codes, write them down (always write them down).  Clear them and road test vehicle again.  Re-scan and lets see if you have an isolated cylinder miss such as a P0305 (miss cylinder 5)on both road tests or random cylinder missfires such as a P0300 (random) or different cylinders on each road test.
 We can work forward from there.

Wayne