98 Chrysler T&C sudden shutdown

When I'm driving on the freeway for a long stretch (200 miles or so),
the van will suddenly go from perfect purr to powerless with a
gas-rich, backfiring idle.
Now here's where it gets weird.
If you disconnect the battery (pre-tested) from both cables and
reattach, it fires right up and runs like new. Problem is, it could be
for 20 miles or another 200. If you do not disconnect the battery, you
can only limp along, backfiring and lurching down the Interstate at
about 3 mph.
Could this be a fuel pump relay, alt relay or somesuch? Or is it an ICM
failure? The battery and coil have tested good, and the random failure
suggests electrical. The only trouble code I can get off it is the
potentially useless -- 12 - Battery input to PCM disconnected during
last 50 key starts.
Any ideas?

 

Sounds like it could be a flakey O2 sensor. If you can, carry a
portable scope with you. Next time the engine does this, check the
output signal on the O2 sensor.

hth