Taylor2424

After changing out my stock DBC 02 Silverado 1500 pcm to a ( guy who sold it, tried to base tune it for my mods)p59 pcm from a 2003 silverado 2500 to run flex fuel and 3 bar capability, I keep getting the dreaded P1518(PCM to TAC Module Serial Data Circuit), causing the truck to go into limp mode (cant accelerate over 1000rpm's or so). What would be causing this? I've already checked all the grounds thoroughly. When putting my stock pcm back in, and turning the truck to the "Run" position, no reduced power mode light comes on. When the p59 pcm is in, it shows the reduced power mode light even before I start the truck. Are the PCM grounds any different? Are some settings/tables wrong on the base tune p59 pcm? I always thought the TAC module was for DBW systems, does that mean the PCM is wrong for my DBC truck? Or can that be swapped over in the tune?

Any input/info would be appreciated