I have had an issue from time to time for the last few years with my 1994 C3500. It has a 454 engine. So every now and then the engine light would come on and it would be accompanied with a temporary increase in idle speed and followed up with a check engine light. First I thought it was because the spark plug wires shorted out by just touching some metal. So I bought wire stand offs. that seemed to have helped but I would still get the engine light to come on every now and then. I got a paper clip as recommended on you tube and read the blinking as pointed out. I located it to be a throttle position sensor 2 blinking followed by 2 blinking or 22. So I ordered a tps from rock auto for 33.99 and installed it and so far so good. we'll see today as I will take it on a test drive.