P0300 error

n8huntsman · February 12, 2005

I have a 2001 Silverado with the 6.0. It has about 30,000 miles. I was recently driving to work in the rain and in traffic and the check engine light started flashing. I drove it the rest of the way to work and home. About 75 miles with the light on. I scanned it when I got home and first it said P0307. I cleared it and scanned again when the light came right back on. The second time it said P0300. I dont want to damage the cat. Should I try some seafoam or what? Do you think the rain might have damaged the o2 sensor? It rained here for 2 weeks straight about a month ago and I never had a problem so I dont think thats what it is but who knows. Any help will be appreciated.

Haulin' 8.1 · February 12, 2005

I have a 2001 Silverado with the 6.0. It has about 30,000 miles. I was recently driving to work in the rain and in traffic and the check engine light started flashing. I drove it the rest of the way to work and home. About 75 miles with the light on. I scanned it when I got home and first it said P0307. I cleared it and scanned again when the light came right back on. The second time it said P0300. I dont want to damage the cat. Should I try some seafoam or what? Do you think the rain might have damaged the o2 sensor? It rained here for 2 weeks straight about a month ago and I never had a problem so I dont think thats what it is but who knows. Any help will be appreciated.

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P-three hundreds are all misfire codes. Three hundred even (0300) is random mifire dectected. This can be set if all cylinders are misfiring at random intervals like with some bad gas or if there's specific cylinder misfiring but not long enough for the ECM to identify it yet. I think this is your case as it had a 7 set before.

A P03xx tells you which cylinder is misfiring, in your case it's number 7. On the Chevy number 7 is the rearmost drivers side cylinder.

Any internal combustion engine needs compressed air, fuel, and spark to burn.

First test for fuel delivery. A mechnics stethoscope can be rigged up by cutting yourself a 1-2 foot piece of heavy wire like from a coat hanger. Make it straight with a small loop on one end. Locate the fuel injector for #7 and start the engine. Hold the loop end of the wire up to your ear and touch the injector with the other end. You should hear constant click-clack noise. This is the injector opening and closing. If not you could have a bad injector or wiring. If no noise test for voltage and ground with a test light at the wire harness connector to injector #7, it should flash with the engine cranking or running. No voltage means check wiring and ECM, voltage but no clicking means bad injector. If it's clicking look for spark.

Spark: with the engine shut off twist and work the #7 plug wire loose from the #7 coil then push it on just enough where it won't fall off then restart the truck. Slowly pull the plug wire away from the coil but no more than an inch or you could get a zap. It should start throwing a strong blue popping spark from the coil to the wire immediatly. It should be able to jump at least a half inch. It may jump to the valve cover, that's ok as long as it's strong. If there is no spark or it's yellow and weak replace that coil. If the coil is making good voltage replace the #7 plug and wire.

This should fix'er up. Do I have to tell you not to rupture your eardrum or get shocked? LOL Common sense is assumed.

Vernon

n8huntsman · February 12, 2005

Injectors are clicking and coils are sparkin. I'm gonna go get a new set of plugs, wires, and seafoam. We'll see if that works, but I'm skeptical. I pulled the plug and it didnt look too bad. It was different than another one on the other bank but, in my opinion, not bad enough to cause a miss. I checked the resistance in the wire and it was only about 150 ohms, so I don't think that is the problem either. But we will see. I also want to add that the check engine light is flashing not solid. At higher rpm's it seems to run fine and the check engine light goes away. When I slow down it comes right back on. Does that mean it's most likely not a fuel problem?

n8huntsman · February 12, 2005

Bought all the stuff and went to dump the sea foam in. Guess what I found! Some dumb ass who filled up the tank last, didn't put the cap back on! Oh yeah, that was me. The bad thing is that the filler is relocated to the wheel well and it was raining. My 40 inch tires kick up a lot of crap that probably got it in the tank. I'm changing the fuel filter and adding the sea-foam. Hopefully that will do it. I really don't want to have to drain the tank. Think I need to?

bob1527 · February 13, 2005

My truck threw a P0307 code today too! And yeah, my decoder said it was Cyl 7 misfire. I did the fuel injector clicking test with a long screwdriver and pulled my plug out. Both look to be working fine. I recently dumped fuel injector and fuel system cleaner in my gas, and i have new plugs on. Im totally lost. Ive been fiddling with it all day. I dont think i have bad gas (in my truck that is).

n8huntsman · February 14, 2005

Pull off the valve cover and make sure you didnt break a valve spring. I read that that happened to someone on here and he was mad because he spent money on plugs wires etc and it still didnt fix it so he took in to the stealer and they found the problem and fixed it and charged him $300 for a spring that costs $2.00 from the stealer. I checked mine, it's not too hard to get to. That was of course before I discovered that my gas cap off.