Looks like my original diagnosis of no power to the coil was correct. Just because you can't see any "fault in the wiring" doesn't mean it doesn't exist. In this case it seems the interruption of 12V power to the coil is in the PCM.

 

40 milliseconds max, sounds reasonable.

I wonder if your crank position sensor is too far from the flywheel. In other words, maybe it was shimmed when mounted and works for most cylinders but is borderline for one or two of them. Also, the characteristics of your van's flywheel might be causing the problem; maybe some metallic debris is partially filling one of the notches. Or maybe the flywheel is out-of-round, i.e., too far from the sensor so the sensor can't detect the difference between the flywheel and the notch. Is it always the same cylinder? Does the code specify the cylinder that's misfiring?

Pictures of my adventures using the oscilloscope on my van are at:
http://www.facebook.com/media/set/?s...1&l=85d45119cc

I have scope traces of cam and crank position sensors in those pictures. I did have some concerns with the falling edge of both signals as well as some other signals; it looks like the voltage falls, then rises again before falling back to 0 volts. It might be an artifact related to the acquisition mode I was using on the scope.

I opened my PCM a few minutes ago. It's mostly filled with a potting compound, probably silicone. The only thing protruding out of the silicone are heat sinks on higher power dissipating components. The silicone potting has large cracks from a combination of the harsh environment in the engine compartment and age. So, I need to find another PCM.

Jeff

 

In the 94 van, the PCM provides 12V to the coil primary by energizing the ASD relay. The PCM also switches the lowside of the coil primary with a lowside driver.

If the 2002 has the same basic relay logic as the 94, then an open-state failure of the PCM's ASD relay driver would deprive the coil of 12V.

Did the dealer say whether the PCM's failure affected the highside or the lowside of the coil primary?

 

What brand PCM did you get? Did you get one at the Dodge dealer? I'm shopping for one and I'd like to get the best brand available for the money.

 

The PCMs are mainly available rebuilt. I got mine from Solopcms.com mainly because they would same-day it, it was 359.00. I would avoid Auto Computer Exchange, they have a rating of F with the BBB and a habit of not shipping parts it seems. The dealer quoted price was 864.00 and they did not have one in stock.

 

One auto parts place has 3 brands; 2 of them are special order items, which means I give them the old one and let them rework it. I'm concerned they won't find the problem because it's intermittent. In other words, they'll test it and find no problem with it, then strip out the silicone potting compound and pour in some new potting compound (that's a "maybe" on both of those), retest it, and send it back to me. My fear is I pay $250 for a box that has the same intermittent problem.

I'd rather take my chances on another PCM. Also, I'm asking a FB friend for advice on repairing and refilling one of these myself. My concern there would be the process for pouring new compound so that moisture wouldn't be trapped inside.

Dealer's price of ~$860 is about what I'd expect.