What is the blue wire by starter on Chevy pickup?

The blue wire by the starter on a Chevy pickup is most likely the starter solenoid's control wire. This wire carries the low-current signal from the ignition switch to activate the solenoid, which then closes the high-current circuit to crank the engine. However, this isn't guaranteed; wiring colors can vary slightly by year and model.

To be absolutely certain:

* Consult your vehicle's wiring diagram: This is the most accurate source of information. You can often find this diagram in your owner's manual or online (many repair manuals have them freely available, searching for your specific year, make, and model).

* Trace the wire: Carefully follow the blue wire from the starter solenoid. See where it connects to determine its function.

* Use a multimeter: With the ignition in the "on" position, check for voltage on the blue wire. If it has voltage, it's likely the control wire. Be extremely careful when working with car wiring and electricity. Disconnect the battery's negative terminal before doing any electrical testing.

Without knowing the specific year and model of your Chevy pickup, a definitive answer is impossible. Always rely on your vehicle's specific wiring diagram for the most accurate information.