93 White GMC with problems help the noob!

93 white GMC aero i bought it for 2K. Problem #1 Previous owner stated it need a gas pedal.CPU would cut out and reset when reving the engine yellow and red stop engine light. After investigating and $$$$ found out that the ECM power and ground wires to the battery was hooked up in correctly. I reconnected everthing now i have a amber check engine giving codes 16 , 23, and 32. i replaced the CLS and this code still appears along with the others. could this be from a faulty ground? Can I re run the ECM ground wire straight from battery to the ECM?? I dont want to throw parts with no remedy

Problem #2 Tachometer . Tach stays on "0"

Problem# 3 Water temp Gauge not working.Could this be the sending unit? Gauge is all the way to the right.

Thanks in Advance
Chad