crainholio

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Last night I took my '01 LS1 equipped '82 Camaro for a spin, after about 15min of ~30-50mph light driving it developed a stumble above ~2500rpms and then lit the SES light. EFILive indicated P0200, the injector circuit voltage variation error. The car has been running since Feb, and has over 4K miles of street driving as well as three one-day road course driving events.

I executed the Helms manual diagnostic procedure, no findings. No individual cylinder misfires while driving, just another P0200. Freeze frame data showed it happened at ~3400rpm.

I tested resistance on all 8 injectors while the engine was still hot, 7 were 14.4-14.6 Ohms and one was 13.2 Ohms. These are the factory '01 injectors that came on the engine when it was pulled from the donor Trans Am, have about 40K miles on them.

I replaced all 8 injectors with my backup set and repeated my earlier driving route...no errors. I drove a little further, still no errors. It was getting late so I headed home and will retest tonight. I re-tested the 8 original injectors after they had cooled, all were 12.4-12.5 Ohms including the oddball one.

Just opening this up for discussion if anyone has any experience or info. Searching here and elsewhere, injector failure seems to be the most common root cause of P0200 by itself, with one case of bad connector wiring and one case of re-flashing the PCM. In this case, my theory is that the one injector has an internal insulation failure which reveals at operating temp...seen it with ignition coils when the insulation around the windings starts to fail...they Ohm out fine cold but drop off when they get hot.

crainholio

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Update: I put a good 45min of road time on it tonight, having changed nothing but the injectors, and got no further DTCs or misbehavior. Last night's DTC set after ~15min of driving.

JoeyGC5

iTrader: (24)

I had the same problem last week with my SVO 30lb'ers. Injector ohm test showed 16.3-16.8 ohms across all 8. Let the car cool for two hours and everything was fine there after I don't know

crainholio

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Update: P0200 is back almost a year later.

Following my original post in June 2004, and subsequently replacing all 8 injectors, I put three all-day road course events and over 2K street miles on the car with no further issues aside from a blown pax side O2 sensor at Pocono North at the end of the season. (since replaced both O2 sensors w/ Denso ones)

I brought the car out of Winter storage a few weeks back for short trips, ran great.

Yesterday was my first highway sprint, after ~10-20min of varied driving I felt it start running slightly rough and sure enough the SES light came on. P0200.

Back at my garage, I cleared the DTC, found two spark plug wires not completely seated (clicked when pushed in) and #1 injector connector not completely seated (clicked when pushed in).

I disconnected, inspected, and re-seated all 8 injector connectors after testing resistance while they were still hot. 13.9 Ohms +/- 0.1 Ohm all around, we're good.

I took the car out again this evening and after 10+ mins of varied driving I felt the slight roughness come back. Scanner showed P0200 in Pending state, PCM operating in CL-Fault mode both banks.

Back at home, all 8 plug wires and injector connectors were still firmly seated...no clicks when checked.

Running the Helms diagnostic procedure, I again got 13.9 +/-0.1 Ohm at all injectors. Voltage checked 12.06 VDC at the batt, and 11.75 VDC at injectors 2,3,4 (just randomly picked a few to test...if this keeps up I'll check them all).

I disconnected, inspected, and reconnected C100, C101, C105, and C207 (underdash connector on my '82 chassis harness). No loose wires or bent pins found.

Reading my logbook, the original P0200 back in June 2004 happened shortly after I swapped back to my stock '01 plug wires...which I was still running. Hmmm...

I checked resistance on all 8 stock wires, 378 Ohms +/- 3 Ohms all around. I pulled my aftermarket wires off the shelf and tested, 26.5 Ohms Ohms with no variation all around. I swapped the aftermarket wires back on, but it's now pouring rain so testing is over for tonight. I'll try it again over the weekend and report back. I've also added the PIDs for misfire detection to my EFILive config so hopefully I'll get a clue as to which specific injector circuit is misbehaving if it does it again.

If it does it again, I'll check voltage at all 8 injector connectors and look for variation. Also thinking of checking resistance across the 8 coils, as they share voltage feeds w/ the injectors and a bad coil could possibly cause voltage variation across the circuit.

Any other ideas or experiences greatly appreciated!

crainholio

iTrader: (2)

Update: I put over 50 miles on it today, no P-codes or recorded cylinder misfires...woo hoo!!

Next time I'm in the wiring harness, I'll break the coil packs off to their own 12VDC fused feeds and separate them from the injectors. That P0200 had nothing to do with the injectors, it was the plug wires but because the coil packs share 12VDC feeds w/ the injectors the problem showed up there.

A_W_O_L

iTrader: (2)

Did you ever get back into the harness and separate the coil packs to their own feeds? I'm having the same DTC but the engine doesn't miss long enough for me to find out which one it is. I usually have just enough time to hit the shoulder and pop the hood (in one motion) and start disconnecting injectors one at at time (usually only get one) before it cleans up and quits missing. It has died on idle while pulling up to an intersection. Feels like there's more than one cylinder missing. I'm at work right now I'll post up more info later tonight.

crainholio

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Man, this one's back from the dead! Sorry you're having that problem, hopefully my experiences might help.

As I posted way back when, the PCM dropped mine into CL-fault mode while P0200 was in pending state. This likely accounted for my misfiring...it never set an individual cylinder misfire code.

I never did separate my coil and injector 12VDC feeds, they're still in factory configuration. I've put two years' worth of leisure driving on the car and haven't seen a DTC (knock on wood) the entire time.

I'm still running the aftermarket plug wires I installed at the time of my posting.

Just to ensure a confirmed kill on this, I later resistance-tested all 8 coils at their 12VDC pos and neg pins and swapped out the one that varied from the rest. It wasn't off by more than ~2 Ohms, but the rest were very consistent so I bought a replacement and verified that it was within ~0.5 Ohms (going by memory here, logbook's buried in the basement at home).

A_W_O_L

iTrader: (2)

I appreciate you posting this problem ...I remember you were going through your swap when I went through mine....and I (until now) haven't had that problem.

After it cools off I'm going to check the plug wires. I'll post up more in a few mins.

A_W_O_L

iTrader: (2)

I haven't had the extra time to post up what I've done so far...however I'm almost convinced that it's the Engine Coolant Temp Sensor causing the problem. In an overtemp situation where there is no coolant present...the computer resorts firing on "reduced" cylinders......does anyone know which cylinders it cuts off? I've heard that it's random...Does anyone know for sure? Would it cut off an entire bank and run on the other?