P0200 Inj circuit Malf caused by spark wire?

[Jetmech442]

Hi guys,
2005 LQ9, LS1 injectors(tables updated), LS1b ecm.
I've read through a LOT of the P0200 threads both here and on LS1tech. I ran the noid lite, ohmed the injectors, traced gound paths. all of those are good. It only starts to act like an idiot after I go WOT and the engine gets real hot.

I figured I would ohm the spark wires(MSD-about 40 hours on them). they all ohms out to 35 ohms, except for one that was 143. I sprayed carb cleaner in it and rechecked--35 ohms. Somehow there was some gunk on the spark end. Do you think this could have been enough to casue the code to pop?

[joecar]

I think that the ignition wires are not directly responsible for the injector circuit DTC...

especially the MSD Superconductor wires (they have very good electrical noise suppression);

if one MSD wire ohms at more that 40 ohms then replace it <--- it has failed.


Check the injector subharness for breakage, shorting, stretching, melting... and check each pin in each connector for good connection...
and check the condition of all engine grounds (that they are all present, and that they have zero voltage drop (no more than 0.1VDC) while engine runs).

Check the ignition subharness for breakage, shorting, stretching, melting.

Is the battery secure (does not flop backward during WOT)...?

Check this: P0200

[Jetmech442]

I think that the ignition wires are not directly responsible for the injector circuit DTC...

especially the MSD Superconductor wires (they have very good electrical noise suppression);

if one MSD wire ohms at more that 40 ohms then replace it <--- it has failed.


Check the injector subharness for breakage, shorting, stretching, melting... and check each pin in each connector for good connection...
and check the condition of all engine grounds (that they are all present, and that they have zero voltage drop (no more than 0.1VDC) while engine runs).

Check the ignition subharness for breakage, shorting, stretching, melting.

Is the battery secure (does not flop backward during WOT)...?

Check this: P0200

Thanks joe. I cleaned the MSD wire, it re-ohmed at 35-reinstalled. All injectors ohm out at ~12.5. The noid light flashes correctly on all 8. I didn't see anything obviously wrong with the harness, so I drove again and logged. I did notice that when I let off the throttle at high rpm it goes very lean(WBLambda ~5-7). Then, at timeframe 5400 everything goes haywire like usual. HO2S11 flatlines at ~400mV while HO2S21 just drops to zero(WBLambda is reading ~1.2 at this point). OH-while typing this, I plotted ECT1-it starts jumping in and out between 198(matches my analog gause), and -35F...thermophysically imposible. okay, unless anyone has any more suggestions, I'm going to spend a few days chasing wires.

[joecar]

I'll take a closer look at the log file tonite...

[Jetmech442]

If you get a sec, can you look at the o2 sensor mV reading? I've been searching here and ls1tech and it seems like the o2 should be switching faster than it is

[joecar]

You're on my queue...

sorry it's taking longer to process my queue, her Dad is in the hospital and we've been spending a lot of time there.

[joecar]

Your NBO2 sensors have a slow CL cylce time, about 1.4-1.6 seconds, this is too slow, they should be cycling at 0.2-0.3 seconds...

PCM does its best to maintain CL, but then at frame 5381 both NBO2's "die"...

looks like what happens when NBO2's get fouled (are you running leaded fuel...?).

ALSO: your ECT circuit has a breakage, see where ECT falls to zero in various places thru-out the log.

[Jetmech442]

Just wanted to go through and close this one out for others that may find it. The ECT dropping to zero was the give away-thanks Joe. I found my wire harness pinched between the transtunnel/cyl head. This was due to my personal routing of the harness.

I replaced both NB02's, and the new ones switch fast, about 3-4 times per second. Oddly, the new ones still flatline...which is causing my Calc.vet procedure to have issues, but I'll start a new thread for that so this one can rest.

[joecar]

If the NBO2S flatline then there's still a problem... check all the ground connections.