I have no idea what caused my misfiring PCM to fail and it is quite uncommon for these to fail but sure enough, it did. The misfire graphic on my NANO Tech2 computer screen was clean and clear. I popped in a 512k byte PCM and BOOM, problem solved, no more misfires. I can also flash the operating system for free in these using Tuner Pro RT (for editing) and LS Droid / PCM Hammer – no money spent on HP Tuners credits or EFI Live fees. And I have four of these 512k byte “P01” PCM devices and two of the 1 megabyte “P59” PCM devices for lab rat experimentation. What’s left to fix on an LS engine with a whole lotta’ random misfires? The powertrain control module (PCM)!! Fortunately for my LS engine, they are cheap in the junk yards at $32 around here and big-time dirt cheap on Half Price Sale Days. And the engine actually ran surprisingly well without shudder during the periods of misfiring. Yet, the spark plugs looked good and I tried swapping coil packs and plug wires without any success. No change – I still had seven cylinders worth of random misfires confirmed with an old school engine timing light – not any false misfire. I also checked the existing wire harness to the PCM bundle of ground wires at the back of the driver’s side head. So I did that with three copper lug soldered half inch braided wire ground cables from the M10 x 1.5 bolt holes in the ends of each cylinder head directly to the negative battery post. With this many misfire problems in an LS engine, we are told to start looking for bad or missing engine grounds and this makes perfectly logical sense. Once I got my NANO device up and running, it turns out that I had a bigger misfire problem than I thought across every cylinder but cylinder 2.

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