2002 4x4 SR5 Check Engine Light (CEL) P0300, 0301, 0308

I thought I would share this experience I had with these codes. With the P300 code, it is a random misfire, and the 301 and 308 were specific cylinders, 1 and 8.

Started with the fuel filter which seemed like the cheapest and most likely culprit, didn't work.

I then checked the spark plugs and they looked a little worn, so replaced all of those, then also noticed a cracked vacuum hose, and replaced the PCV valve, which originally other posts seemed to say that there was an EGR valve, which my truck did not have. These things fixed it. Not
bad for less than $100. YMMV

 

I'd call it an inexpensive fix.

 

How’d that PCV valve cover chamber look when you took it out? Mine was gunked! Glad you solved your problem and thanks for the follow up.

 

Hmm, I just changed the valve, didn't poke around inside the cover. Maybe I should?

 

Ye mate. Only reason I saw mine all gunky was because I was doing the VC gaskets and had the covers off. That PCV grommet was toast and fell in. Looked in the hole and thick oil paste! Blasted it with Cleaner.

I think if I was NOT doing the VC gaskets and my port chamber was clogged I’d try to scoop out as much as possible (difficult) using a popsicle stick. Then slowly over the course of a few weeks on a daily basis put a few drops of your motor oil or a quick 1/2 second blast of PB Penetrator in that port to dissolve it slowly back down into the valve chamber oil and circulated into the oil filter.