To find the tachometer wire, you'll need to:
* Consult a wiring diagram: This is the most reliable method. A wiring diagram specific to your truck's year, engine, and options will show you the correct wire color and location. You can often find these diagrams online (though be cautious about the source's accuracy) or through a repair manual specific to your vehicle.
* Use a multimeter: With the ignition on, carefully probe wires at the back of the instrument cluster or at the engine's computer (ECU) while monitoring the multimeter for a pulsed signal that corresponds to engine RPM. This requires some automotive electrical knowledge and caution to avoid short circuits. Never probe wires with the ignition off.
Without a wiring diagram specific to your truck, determining the color is impossible. Attempting to guess based on general information is risky and could damage your vehicle's electrical system.
