need some help guys. this all started with nox sensor replacement, the back nox sensor was badly rusted, long story short on that, i had to relocate the nox sensors due to the bad port being broken, i put 1 on the front passenger side head and the other on driver side block between 3 and 5 exhaust, after doing that i replaced spark plugs, coils and wires. also had code for evap canister, no power to the canister by fuel tank, i found the break in wire and ran another wire for power,

now for the problem i cant figure out, after doing the above about 2 weeks later i started getting p200 and p307 codes, only after it either idles an extended period of time, i could let it sit for 15 to 20 mins and clear the code and wouldnt come back on for a few days, i ut a node light on the injector even when it is misfiring and seems to be firing normal. i have swapped cyl 7 plug, coil and wire to cyl 3 to see if it changed,, it didnt stil cyl 7. got any suggestions on what to look at.

 

Year, Make, Model, Engine.

What is a nox sensor? Do you mean an Oxygen sensor?

Remember DTCs tell you there is a problem with a circuit or a system. Not that a specific part is bad.

P0200 is telling you that there is a problem with a fuel injector control circuit.

Good Luck!

 

guess i did forget to put truck info,, 2005 silverado 5.3l

knock senosr is what i meant by nox.
i did replace the o2 sensors for the hell of it yesterday,

cylinder 7 is only one that is misfiring accordin to live data on my tablet,

 

Thanks for letting me know what you meant by nox sensor. nox generally refers to nitrogen oxides - a component of vehicle exhaust gases.

Based on the P0307 and P0200 codes, I would carefully look at the wires going to the #7 fuel injector and the connector itself. Make sure the wires are intact going into the connector, that there are no bent pins on the fuel injector, that the contacts inside the connector are clean, and that the connector is properly seated onto the fuel injector.

You might have broken a wire when putting things back together. I know because I did and I wound up replacing the #7 fuel injector connector when I replaced the knock sensors on our 1999 Silverado a few years back. Amazing how easily one of the wires broke.

Since you already swapped the coils and plug wires for cylinders #7 and #3 you can rule out the ignition coils and plug wires. What about the spark plugs themselves?

Good Luck!

 

i took the wire loom off and cant see anywhere that looks like damage to the wiring, the connector appears to be fine,, i already swapped plugs as well.

guess next step is replacing injector to try and eliminate that,,

 

Save your money and diagnose first!!!!

I would just swap the #7 injector with the #3 injector. If the misfire code changes to P0303, then you know it's a bad injector. If the code stays P0307, you know you have a wiring problem to the #7 injector.

Good Luck!

 

i "liked" the post about switching injectors until i remembered THEY AREN'T EASY TO SWITCH like on an asian car. (you have to take off the intake and "get in there", and if you break it it's expensive - and they are't packaged individually like asian cars. there's a pump assembly and a spider assy)

BE PREPARED: many chevy had to have head gasket. RE: mexico ASSY PLANT used a plastic head gasket. Canada sold GM acidic recycled radiator fluid as "new" (orange) (i use only prestone non-recycled due to this !!). if this car's history never had it done, it may need it.

indications: "water in oil". "one cylinder gets misfire". "seems to run a little rough"

I'm saying "look into that" because no point in taking off the intake to get to injectors and finding the job is much bigger than you thought.

When I did mine i had a dead injector on the CYL that radiator fluid was getting into. bought a whole new injector+spider assy. the dang injector cleaner, 3 days later, had fixed the dead injector clean and working (too late! already had new one installed