Don't overlook the possibility of your PCM failure being caused by something like the
engine compartment getting too hot, a cable/connector loose or has a pushed out pin,
battery voltage dropping out, etc.   For example my Durango developed a heat sensitive
problem that was eventually resolved by lowering the engine compartment temp by a number
of "mods" to improve airflow and route the engine/radiator heat outside of the vehicle as
quickly as possible.  My PCM was replaced also because of the heatup/cooldown cycling that
had (apparently) caused the failure to rear it's ugly code.  The code that was being set
was caught at the dash computer and indicated "no bus" which means it could not
communicate with the other controllers that it normally exchanges data with.  In a valiant
effort to "protect" me and the vehicle I guess, it (The PCM) also would pick the relay
that shuts down power to most of the vehicle until the "PCM" was allowed to cool off.
Just using this to illustrate that identifying the  failing assembly is (in some
instances) a far cry from being a straight forward process.  Good luck in identifying  and
fixing your problem.  I have found the factory service manual to be extremely useful in
understanding and resolving these types of issues.  Just curious and I apologize in
advance if I missed it in a earlier post but what motor does your rig have?  best regards,
Joe.

Joe Brophy
CountryTech Computer
email: pcfixr@spiretech.com