Q: What are relays and how are they used in Chevrolet Avalanche,Silverado,Suburban,Tahoe,GMC Sierra,Yukon,Yukon Denali and Yukon XL?
A: Relays are used in several electrical circuits in vehicles to transmit electrical signals to components. They use a low-current control circuit to open and close a high-current power circuit. If a relay is defective, the corresponding component will not function properly. Most relays are located in the engine compartment Fuse/relay box, with some specialized relays located above the interior fuse box in the dash. To test a suspected faulty relay, it can be removed and tested using an ohmmeter to check continuity through the relay control coil and power circuit terminals. The terminals of ISO relays are numbered to indicate their usual circuit connections and functions. If the relay fails any of the tests, it must be replaced as a unit.