I have an 03 Suburban 5.3 with about 120xxx miles and haven't had much issue. Suddenly started almost falling on its face no power, hesitant almost sputtering engine light came on and as I got almost home at 20mph the engine light started flashing. Threw codes p0101, p0300 and p0420...101 has come up before and I changed the MAF sensor and it didn't change anything and we have pretty much ruled that out. I've read tons of things like clogged cats and everything else. Tested the fuel pressure today and it tested about 42 with a peak of 45 and from what I see this truck needs 50-55. Sooooo....fuel pump ? Any opinions on this throwing me those codes ? I will try the filter too but I doubt that could cause it unless it's totally blocked which I doubt. Fuel also looked a little dirty when testing pressure. Just trying to make the most wise choices as I can't afford to just replace any and everything and need to make it count and also need this truck back up! Thanks for any opinions!

 

is there a rotten egg smell at all when its running? before the light started flashing? The p0101 could be causing the 300 and possibly 420, Need to start there and get that code handled unless you have a scanner capable of showing misfire data to check for a dead miss.

 

No rotten egg smell. Honestly I have had p0101 come and go for quite a while now starting immediately after adding Spectre cai. I'm gathering parts to start trial and error with the fuel pump being delivered tomorrow. Also got a fuel filter which I doubt is a cause and fuel pressure regulator.

 

...on second thought...just when it got really bad I did suddenly smell something and I couldn't identify it and it worried me given how the truck just started performing but I wasn't sure if it was the truck or an outside smell. I parked it for about ten mins and didn't smell anything until I came back out. I could still faintly smell it IN the truck but not outside. I then drove it a very short distance back home and didn't smell it again so I assumed it wasn't the truck. It wasn't rotten egg but it was definitely a strange smell.
Also just when I parked it before I turned it off (during the smell) I thought I heard some faint metallic "rattle" coming from under the truck that was very brief. Now thinking maybe it was the cat I smelled and heard bits rattling around in it/them.