In the vehicle, various electrical accessories such as the fuel injection system, horns, starter, and fog lamps utilize relays to transmit electrical signals to their respective components. Relays work by using a low-current control circuit to open and close a high-current power circuit, enabling the proper operation of these components. Most relays can be found in the engine compartment and interior fuse/relay boxes. If a faulty relay is suspected, it can be tested using the following procedure or taken to a dealer service department or repair shop for evaluation. The relays used in these vehicles are typically ISO relays, adhering to International Standards Organization standards. They have numbered terminals indicating their circuit connections and functions. Two of the relay terminals are for the control circuit, connecting to the relay coil, while the other terminals serve as the power circuit. When energized, the relay's coil creates a magnetic field that closes the larger contacts of the power circuit, providing power to the circuit loads. Terminal 85 and 86 are usually the control circuit, with terminal 86 connected to battery positive (B+) voltage and terminal 85 to ground in relays with diode terminals. If the relay contains a resistor, terminals 85 and 86 can be connected in either direction with respect to B+ and ground. Terminal 30 is typically connected to the battery voltage source (B+) for the circuit loads, and terminal 87 is connected to the ground side of the circuit, either directly or through a load. Relays may have additional terminals, such as 87A, 87B, 87C, etc., for alternate load or ground connections. To test the relay, use an ohmmeter to check continuity through the relay control coil and ensure resistance matches the expected value. If the relay fails the tests or shows infinite resistance, it should be replaced. Additionally, when testing the relay's power circuit terminals, there should be no continuity between terminals 30 and 87 with the relay de-energized, but there should be continuity when the relay is energized using jumper wires. If any of the tests indicate a failure, the relay should be replaced.
Posted by GMPartsGiant Specialist