I installed a reman FICM from ficm.com in september and the truck runs a lot better. however, it will occasionally and randomly run rough and eventually sets code p0263 and p0275. Do I automatically condemn the FICM or might something else cause the problem?

I am un-clear on how cylinder contribution is calculated and what would cause such a codes.

 

Cylinder 1 & 5 contribution balance codes is more likely injectors than FICM.

 

Or a shorted wire in the inject harness since you have random drivability issues

First thing I would try is making sure the inject wire harness is FULLY pluged into those 2 inject and the ficm especially since both DTC are coming from same ficm plug


Then start the truck and wiggle test harness see if you can force it to run rough

 

I agree with Benny. The big clue is the fact that you say intermittent.
Start with the plugs on the FICM and then check each injector plug.
Last look at how the harness lays on the engine. Your looking for pinch,crush
and rub points anywhere. One thing to not over look is sharp bent wires.

Sean