The coil doesn't set a code of it's own. The code is P0300 - multiple> misfire, which a bad coil could cause.

96 Chevrolet C1500 1/2 ton truck, 4.3l 6 cyl

When the coil is cold it reads as follows:> Primary: .1 @ Secondary: 5.86K

Engine at operating temperature:> Primary: 2.9 Secondary: 6.33K

Hi, people>

I am slowly trying to run down the cause of an intermittent misfire on> the truck above. It gets warm, then the MIL comes on and it starts> running bad. I have replaced plugs, wires, cap & rotor. The ignition> module checked out OK. Can't find any vacumn leak by physically> observing. Now I am checking the coil. According to the Wells manual at> Auto Zone, the secondary should read 5000 to 25000 ohms and the primary> should read .1 ohm.>

When the coil is cold it reads as follows:> Primary: .1 @ 200 meter setting> Secondary: 5.86 @ 20k setting>

Engine at operating temperature:> Primary: 2.9 @ 200 meter setting> Secondary: 6.33 @ 20k setting>

The primary resistance is 3 times what is expected when the coil is> hot. Does this mean it is really good or really bad?>

Thanks,> Libby>

If you used a regular spark tester, the kind where you unplug the boot> and put it on the tester, on a DIS ignition system, would the companion> plug still fire? I'm going to try it one day, just out of curiousity.> It is interesting.

If you were doing a cylinder balance test on a vehicle with DIS> ignition, pulling one plug-wire would kill two cylinders?

But, as long as you used a spark tester, the companion cylinder would> still fire.

I guess you would have to kill the engine everytime you changed plug> wires and restart. I wouldn't want to handle the wire with the engine> running, I tried that before, that stuff has a bite to it. I was even> holding an insulated screwdriver handle, still got me. I was dancing a> jig hollering at the helper to turn the key off. The vehicle was OBD1.> thanks