GMC Yukon Cooling Fan Relay Location by Model Year

Where the cooling fan relays sit on a 2015 or 2016 Yukon

The 2015 and 2016 Yukon and Yukon XL belong to the same generation, so the location is the same for both years. Open the hood and look at the driver's side of the engine bay, beside the battery. The black box with a removable cover is the underhood fuse block, also called the underhood electrical center. It houses the cooling fan relays and the fuses that feed the fan motors. Release the cover latches and turn the lid over. Its underside carries a chart that names each fuse and relay position. The fuse and relay table in the owner's manual typically shows the same layout. Use the manual if the lid label is worn or the lid may have come from another vehicle.

More than one position may be labeled for the cooling fans, because dual-fan systems often use separate relays for low-speed and high-speed operation. A neighboring relay with the same shape is not necessarily a fan relay. Read the label for the exact position before pulling anything.

How the fan relays control the fans

The fans on this generation are electric, and a temperature sensor does not switch them directly. The engine control module reads inputs such as engine coolant temperature and air conditioning refrigerant pressure, then decides when the fans should run. To turn them on, it energizes the relay's control coil, usually by completing the coil circuit to ground. The relay then closes a heavy-duty contact that sends battery current through a fuse to the fan motors.

This design keeps the large fan current away from the control module. The coil side draws very little current, while the switched side carries the full motor load. On many GM dual-fan layouts, one relay combination runs the fans in series for low speed and another switches them to parallel for high speed. That is why one failed relay can leave the fans working on high but never on low, or the reverse. A blown fuse, a corroded connector, a weak ground or a faulty control module output can cause the same symptoms, so the relay is only one of several suspects.

What changes the answer

Model year matters most at generation boundaries. The 2015 and 2016 trucks share an electrical layout. Earlier and later Yukon generations use different fuse blocks, and some use different fan arrangements, so do not use another generation's diagram for these years. Within 2015 and 2016, the engine (the 5.3-liter or the 6.2-liter offered on Denali) and optional equipment can affect which positions are populated. Confirm the details with the label on the specific vehicle.

Some relays in modern GM fuse blocks are built into the block instead of plugging in. If the label shows a fan relay position but there is no removable relay in that slot, the relay may be integrated. In that case, repair can mean replacing the fuse block or following a factory repair procedure rather than swapping a relay. The 2015 and 2016 Yukon also run on a conventional 12-volt system only. The Yukon Hybrid, with its high-voltage traction battery and orange cabling, belonged to the earlier generation and is not covered here. Its procedures and hazards are different and call for trained service.

Isolating the circuit before you work

Park on level ground, shut the engine off, and make sure the ignition is fully off. Let the engine cool. The fans can start whenever the control module commands them, including with the ignition on or while the engine is hot, so keep fingers, tools and loose clothing away from the fan shroud. You can pull or swap a relay with the ignition off. Before probing harness connectors near the fans, unplugging a fan motor or repairing wiring, disconnect the negative battery cable and secure it away from the post. Radio presets and some learned settings may reset afterward.

Checking the relay and fan circuit

Start with what you can observe. With the engine fully warm and the air conditioning set to maximum, the fans usually come on at some point. If they never run and the temperature gauge climbs, stop driving and investigate. Check the fuses that feed the fans, and make sure any replacement matches the fuse rating printed on the label. For a quick relay test, swap the suspect relay with one from a non-critical circuit that has the same part number. If the fans start working and the other circuit starts misbehaving, the original relay is likely faulty.

A scan tool with GM bidirectional controls can command the fans on and off. That tells you whether the problem is in the command or in the power circuit. With a multimeter, measure system voltage at the battery terminals. Then compare it with the voltage at the fan connector while the fans are commanded on. A large voltage drop points to a poor connection, corroded terminal or weak ground rather than a bad motor. If the fans keep running well beyond the normal run-on after shutdown, a stuck relay may be creating a parasitic draw that can leave the battery flat.

Keep the charging system in mind as well. The fans are among the largest electrical loads on the truck, so weak charging output or a tired battery can make fan behavior look erratic. Rule out low system voltage before replacing parts.

Limitations and when to get help

This guide does not give slot numbers, relay part numbers or wire colors, because they depend on the exact build. Guessing from a photo of another truck is a common way to replace the wrong part. The lid label, the owner's manual and a factory wiring diagram for the specific VIN are the authoritative references. A diagram matters most when the relay and fuses test good but the fans still do not respond. The remaining causes then include harness damage, a failed fan motor and a control module fault.

If the engine is overheating, the fans run constantly, or a related trouble code is stored, have the system diagnosed before driving further. A technician with factory service information can command each fan stage and read the coolant temperature data the module is using. That confirms whether the fault is in the relay, the wiring or the module itself.