Testing tach wire???

What should the tach wire test theres four of the same color so when I go to test it how should the right one read? thanks

What type of Vehicle?

Between 1 and 6 volts AC and increase when the gas is pressed. Yes I mean AC, not DC.J Rilla

Owner/Installer

its on a 2002 chevy 1500 suppose to be a white wire and theres about 4 of them.

 Look for the wire at the ECM which 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', and VSS wire is at pin 3 in the connector labeled 'black'. On the 4.8L, 5.3L, and 6.0L, the tach wire is located at pin 10 in the 'red' connector, and VSS wire is located in pin 50 of the 'red' connector.  Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

easiest way is by using an ANALOG vm and test the wire at the coil, or a non-common wire at the injectors.  accelerate and you will see the needle moving showing you difference in AC voltage. Will look like your RPM meter inside your vehicle, goes up as you accelerate ,and go down as you de-accelerate. piece of cake

I've used injector wires on most of those new chevy's....is this wrong? I've heard that some brands recognize injector wires better than a coil wire and vice versa, who's right?!