this code deals with a communication problem between the display and the logics
-check your cable and connections
-check the display for damage
-check the logics for damage
check the following wires for continuity
P3-4 to P6-4 (wire #12)
P3-5 to P6-3 (wire #16)
P6-2 to key switch (wire #4)
P6-1 to battery negative (wire #1)
P3-18 to key switch (wire #4)
P3-20, P3-21, P1-21 to battery negative (wire #1)
If all above checks ok then:
check for short to battery negative (wire#1) in the following wires:
wire #12
wire #16
wire #4
if any check shorted repair or replace wiring

Now from here it says to connect a spare display and turn on the key, if it checks NOT ok then fix shorts, if it does display properly then replace the logics.
So if you have another unit there like that one, remove the display out of it and plug it into this truck and see if that fixes the display or not (after you do all the previous tests.