check engine light 2006 gmc 1500

[traxxas5308]

I have a 2006 gmc Sierra 1500 with the flex fuel 5.3l vortec. A few weeks ago I had a check engine light turn on for p0175 (system to rich bank 2), the light turned off the next day. now about 2 weeks later it turned back on with p0172 (same code except it is bank 1). Any Idea why my truck is throwing these codes, or what it might take to repair it? Any help is appreciated, thanks.

[rjgti]

what are your o2 zero crosses at?

[traxxas5308]

I would have to check on that. I did figure out it is fuel pump related. I have the flex fuel EFI model. It should be running at 48-52psi at the fuel rail, and mine is running at 62. Now what is special about the flex fuel model is it has no return line to the tank, The pressure is all regulated through the pump. So I could have a bad pressure sensor, or else if the regulator is bad in that case I will have to replace the pump.

[rjgti]

that would do it, glad ya found it

[txab]

I would have to check on that. I did figure out it is fuel pump related. I have the flex fuel EFI model. It should be running at 48-52psi at the fuel rail, and mine is running at 62. Now what is special about the flex fuel model is it has no return line to the tank, The pressure is all regulated through the pump. So I could have a bad pressure sensor, or else if the regulator is bad in that case I will have to replace the pump.

Return-less fuel system is not "special" for Flex fuel. It came into being in '04 when the fuel filter was removed from the frame rail. Double check you specs for your fuel pressure reading. Key on engine off reading

[traxxas5308]

While driving tonight I had the light go out, so when I got home I got the fuel pressure tester out. It still read 62 psi with the light out, however it only took a couple minutes in the driveway for the light to come back on. At idle I get 62 psi. With the engine off and turning the key on the gauge reads 62 psi while the pump is priming, after the pump shuts off it sits steadily at 56psi. The spec for the vin code Z engine (what I have) is 48-54 psi.

[rjgti]

more volume at higher pressure for same pulse width= rich

[traxxas5308]

I have now picked up a P0300 code also which is for random misfire

[traxxas5308]

I found someone with a snap on code reader and my misfires are on cylinders 6 and 8.

[traxxas5308]

update: I was able to diagnose the misfire as the cylinder 6 fuel injector, replaced it and the misfire went away. however after clearing the p0172 and 0175 code the light still comes back