guage problems

I'm working on a '98 bravada, someone recently put a new engine in and brought it to me to figure out the problems. the fuel and temp guages do not work, the MIL is on as well as the security and battery lights. I've tested about everything obvious and all is ok. does anyone have any ideas? I'm leaning towards the brain.

Should have battery voltage at all times on the red wire on the rear of the alternator. The brown wire on the alternator should have battery voltage when the key is in the RUN position only. Might be a fusible link not connected or have an open circuit in it. What DTC's are in memory?

It actually runs fine and can't get a scanner to communicate with it,