P0200 and P0300
 

Hi guys. Hoping you can help me. Bought my 2001 Chevy Blazer at an auction, have replaced the idler arm, pitman arm, radiator, ABS control module and lower intake manifold gasket so far. I left work last night and noticed she was idling rough, and SES light starts blinking. I had a Bluetooth scanner in my glove box, pulled a P0200 and a P0300 after I drove home.

Really trying to avoid the mechanic, my wallet is still kind of sore. What diagnosing steps should I take?

Well the po300 is random miss fire so I would look at plugs and wires possibly cap and rotor as well that may be whats throwing both codes, But only use AC Delco parts as these vehicles Do NOT like after market parts

the p0200 code is an injector circuit malfunction code. the p0300 (random/multiple missfire) is the result of the injector issue and may not be a problem in itself. an open or shorted injector, wiring problem at the connector on the manifold, or an ecm issue can all be the culprits. if you can get your hands on a non contact thermometer (pyrometer) you can check the exhaust manifold ports to find which cylinder is cold (the missfire cylinder) and greatly narrow down the wiring to check.

So I replaced the cap and rotor, cleared the codes, and ran it for a few miles. Everything was good, codes didn't come back. Just went out to start it after it sitting about 8 hours, and it's acting up again but the SES light hasn't came on yet. Going to do plugs, wires, and fuel filter tomorrow.

Here save yourself some trouble & possible wasted money!!!! Do a fuel pressure leak down test:icon_couch: trust me on this...any amount of research here will tell u the spider assy on these trks are junk :icon_rant:

So, it's cylinder 1 that is misfiring now according to the scan. (Yes, I scan codes wayy too much). Narrowing it down

I may try a leak down test tomorrow.