99-02 pcm
In the LS1 Harness the Wire for the Speedo, Tach, and Oil Pressure is there, you just have to find them. To get the one for the Volt Gauge just splice into the Red Alternator Wire that goes from the Alternator to the PCM and run that splice to the Gauges.
For the Water Temp Gauge get ahold of a 3-wire Connector like the one that goes to the TPS. Go to the Dealership and buy part #12551708, that is the 1998 LS1 Temp Sensor. Wire the 2 bottom ones in where the original 2 Sensor wires were in the LS1 Harness, and the 3rd top wire goes to the Gauges(once you see it you will know what I mean).
For the Fuel Gauge, leave the Fuel System ALONE..don't **** with any of that going to the gauges..it's fine the way it is. Many people have a mis-conception on this and don't understand how it's wired on the car.






