Vortec 6.0 running rough

[chilson450]

I'm helping my brother out with his 03 Chevy 2500hd with a 6.0 gas. It recently started running rough and misfiring. He put new Delco plugs and wires in it. Fuel pressure is a tad low at 48 psi while idling. Jumps up to 55 with regulator vacuum line off. Sometimes it barely runs and won't even move itself and other times you can't even tell it's misfiring. Watching some data is what is confusing me. Like if I watch the engine coolant temp it will run the correct engine temp and then it will jump to -30 for a second then goes back to normal. Other sensors were acting this way as well. It will go into closed loop and then it flashes open loop fault. I'm guessing something is either shorting out or a sensor is screwing up the others. We're just working with a generic code reader that can watch live data. Any ideas to check on this truck? Thanks for any help.

 

[chilson450]

Forgot to say fuel trims are high positive. He also has lean codes and random misfire code .

 

[Hirev]

1st part almost sounds like a ground issue or 2.

 

[wander2039]

On the 04 Express the o2 sensor wires run on the back of block. Might be different on the truck but if those get disturbed and rub on the block it'll cause those symptoms. The same 5v must be used on all the sensors for that year.

 

[grasscutter]

What are the actual stored codes if I may ask?

 

[JavierH19]

if I watch the engine coolant temp it will run the correct engine temp and then it will jump to -30 for a second then goes back to normal. Other sensors were acting this way as well. It will go into closed loop and then it flashes open loop fault. I'm guessing something is either shorting out or a sensor is screwing up the others. We're just working with a generic code reader that can watch live data. Any ideas to check on this truck?

Sounds like a ground issue. The computer seeing -30 will want to dump fuel to make it run rich since that's what it's supposed to and the trims will go very positive and run like crap with so much gas. And yes what codes. Rarely do the codes actually tell you what can be the fix with an electrical issue but they can sometimes lead you to a branch in the wiring.

 

[Snagglefoot]

LS engines often have ground issues. Check the main ground from the passenger head to the frame. There are also other grounds between the engine and body panels. If there is some corrosion present, clean up where they meet. It there is corrosion within the wire windings, new ground cables are cheap on Rock Auto.

 

[chilson450]

P0300 random misfire
P0174 System too lean bank 2
P0171 fuel trim system lean bank 1
P0327 knock sensor low input
P0c0b drive motor a circuit
P0134 02 sensor no activity

 

[xspeedy]

I’m no expert so forgive me. But the O2 no activity could cause the others? Faulty sensor? Or sensor lost power?

 

[PontiacHO]

Don’t rule out the necessary grounds as has been mentioned but also ensure the battery and alternator are showing normal voltage and charging respectively.