yep kevin, i've seen the same things
if you've ever seen the inside of these relay/fuse box's they are constructed in such a way that there are metal bars sandwiched between insulators internally. I've seen these bars break and rub through the insulators and short out causing a miriad of problems before. The only explanation we could figure out is vibration caused it.
I had a tech at the local cocacola plant show me this after they had went round and round with a couple of thier lifts until they figured it out.
Apparently moving the relays or fuses will let it work again for a short period of time. Its not a frequently common problem but i've seen it more than i'd like to. The most common issues i've seen tho is just faulty relays or bad connections at various places in the harness or on the truck where connections terminate on the frame or at a connector.

and edward is also right, if its an LPS truck then that disconnect box has been known to cause some strange issues, the most common one i've seen is not charging though, not many random codes per say, just the charging issue.

is this an LPS protected truck? what is the voltage of the alternator, and does it hold voltage under load?
multiple codes are sometimes the result of bad grounds, or bad alt output, a loose alt belt can set multiple codes as the voltage goes down while running under load (headlights on?). the LPS shut off box (if so equipped) has been known to not reset completely and properly after someone pulls the cable to see what it does then shoves it back almost into the correct position, which can mimic a bad ground under a load.

dont know if it is the relays going bad themselves or fretting(micro corrossion) on the relay connections,have had this and just pulled the relay and plugged it back in and was enough to clean the connection and clear it up,also same with the ECM connector

yep kevin is right on the money there
bad relays have been problems in the past with these systems
swap them around and see if the problem changes or goes away
in the lid of the relay box it should tell you which relays are the EGI relays which are usually the culprits causing those error codes

i'd also check the ground to frame where it bolts to the frame behind the ecm. Physically remove the bolt and check for painted surface underneath, some units had issues with ecm communication errors and we found that the surface was painted over and we had to scrape the paint off to get a decent ground to the system to get the errors to go away.

E34 is ignitioncircuit malfunction
P04 is ECM Communication error
F04 is ECM Communication malfunction
First thing i would check is that all the relays are seated good in their sockets pull them and push them back in tightly. Would also check the connector(s) going to the ECM to make sure they are tight,pull them also and plug it back in and make sure the latch is tight. Also check the alternator belt and load test the battery to make sure its ok