Tach wire, 2000 GMC Sierra?

"I heard rumor that you can put the meter on AC and meter across ground & the suspected tach wire. Anyone know for sure? " Correct, you should get a reading between 1-8 volts when you press on the gas pedal. DIRECTWIRE™ WIRING INFORMATION - GMC / SIERRA / 2000 / Remote Start 12volts red   +   ignition harness Starter yellow   +   ignition harness Second Starter           Ignition pink   +   ignition harness Second Ignition white   +   ignition harness Notes: To avoid the check engine light from coming on and possible damage to the automatic transmission, the second ignition in this vehicle MUST be powered when adding a remote start system. Third Ignition           Accessory orange   +   ignition harness Second Accessory           Keysense           Power Lock lt. blue   +   brown plug at BCM Notes: The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Power Unlock white   +   brown plug at BCM Notes: The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Lock Motor gray      driver kick panel Unlock Motor tan      driver kick panel Parking Lights+ brown   +   lt. blue plug at BCM Notes: The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Parking Lights- white   -   lt. blue plug at BCM Notes: The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Hazards           Turn Signal(L)           Turn Signal(R)           Reverse Light           Door Trigger     -   BCM Notes: Use tan for the drivers door located in pin B4 of the purple plug, and for the passenger door it will be a orange in pin B2 in the purple plug or dk.blue/white in pin B11 of the lt.blue plug, must diode isolate these wires. The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Dome Supervision           Trunk/Hatch Pin           Hood Pin           Trunk/Hatch Release           Power Sliding Door           Factory Alarm Arm           Factory Alarm Disarm lt. green   -   driver kick panel Notes: Also found in the purple plug of the BCM. Disarm No Unlock           Tachometer white   ac   ECM Notes: ECM is located near the battery, down low, between the fender and the fan under the black plastic cover. On the 4.3L, the tach wire is at pin 20 in the connector labeled red. On the 4.8L, 5.3L, and 6.0L, the tach wire is located at pin 10 in the red connector. Wait to start dk. blue   -   instrument cluster Notes: See DirectFax document 1090. Brake Wire white   +   brake pedal switch Parking Brake           Horn Trigger black   -   brown plug at BCM Notes: The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. Memory Seat 1           Memory Seat 2           Memory Seat 3           Interface Module: Category: Immobilizer Bypass Required: Yes Type: Passlock II Part #: 556LW Alternate Part1 #: 555LW Alternate Part2 #: 555T Notes: Interface Module: Category: Door Lock Interface Required: No Type: N/A Part #: N/A Notes: Interface Module: Category: Combo Interface Required: Yes Type: Data Bus Part #: 457GW Notes: Can use the 457GW to bypass the Passlock II, but it will not control the door locks on this model year.        This wiring information is being provided free of charge on an "as is" basis, without any representation or warranty. It is your responsibility to verify any circuit before interfacing with it using a digital multimeter. Directed electronics, Inc. assumes no responsibility with regards to the accuracy or currency of this information. Proper installation in every case is and remains the responsibility of the installer. DEI assumes no liability or responsibility resulting from improper installation, even in reliance upon this information. Be careful whose advice you buy, but be patient with those who supply it.