Tach wiring for 99+ Vortec/LS
Some PCM's tach signal is not strong enough for some aftermarket tach's. All you do is hook one end of a 1000 ohm (1K OHM) (BROWN/BLACK/RED) resistor to the tach wire, and other end of resistor to fused key 12v+. The tach wire is found on the RED PCM connector for 1999-2002 vehicles and the GREEN PCM connector on 2003-2006 vehicles, Both Pin 10