2015 Toyota Highlander Serpentine Belt Routing, Length & Part Numbers

As an ASE-certified master technician, I’ve replaced countless drive belts on Toyota's reliable 3.5L 2GR-FE V6 engine. The 2015 Toyota Highlander is an incredibly popular family hauler, and keeping its serpentine belt system in top shape is crucial for powering the alternator, water pump, and A/C compressor. (Note: The 2015 Highlander utilizes Electric Power Steering, so there is no power steering pump on this belt routing).

Whether you have the common 3.5L V6 or the 2.7L 4-cylinder engine, having the right parts and routing diagram is essential. Below is your comprehensive guide to the 2015 Toyota Highlander serpentine belt system, focusing primarily on the 3.5L V6 model.

Quick answer

Here are the essential specifications and part numbers for the 2015 Toyota Highlander 3.5L V6:

• Belt Rib Count: 7-rib
• Belt Length: 82.4 inches (approximate effective length)
• OEM Belt Part Number: Toyota 90916-A2023 (or 90916-02680)
• Aftermarket Belt Cross-References: Gates K070824, Dayco 5070825, Continental 4070825
• Auto-Tensioner Assembly Part Number: Toyota 16620-31012 (Gates 38411)
• Idler Pulley Part Number(s): Toyota 16604-31020 (Upper/Lower)

Note: If you have the 2.7L 4-cylinder (1AR-FE), you will need a 6-rib belt (Gates K060480 or similar), and the routing/tensioner will differ.

Belt routing

Since we cannot render an image here, follow this text-based step-by-step description of the routing path for the 3.5L V6. Always take a photograph of your existing belt before removal! This is the best way to ensure you get it right if you get turned around.

Starting from the bottom and working clockwise:

1. Crankshaft Pulley: The belt wraps around the bottom of the large grooved crankshaft pulley.
2. A/C Compressor: From the crank, the belt goes straight up to wrap around the outside of the A/C compressor pulley.
3. Alternator: The belt continues up to wrap over the top of the grooved alternator pulley.
4. Upper Idler Pulley: From the alternator, the smooth back-side of the belt routes under the upper smooth idler pulley.
5. Water Pump: The grooved side of the belt then wraps over the top of the water pump pulley.
6. Lower Idler Pulley: The smooth back-side of the belt routes under the lower smooth idler pulley.
7. Auto-Tensioner: Finally, the belt loops over the grooved tensioner pulley before heading back down to the crankshaft.

How to replace the serpentine belt

Replacing the belt on the 3.5L V6 Highlander is straightforward but working space on the passenger side of the engine bay is tight.

1. Locate the tensioner: The auto-tensioner is located on the passenger side of the engine, below the alternator. It has a 14mm hex cast into the tensioner arm specifically for leverage.
2. Release the tension: Use a long-handled 14mm wrench, a serpentine belt tool with a 14mm crowfoot, or a 3/8" breaker bar with a shallow 14mm socket. Turn the tensioner counter-clockwise (towards the front/top of the vehicle) to relieve tension on the belt.
3. Remove the belt: While holding the tensioner back, slip the belt off the easiest accessible pulley (usually the top alternator pulley or water pump). Slowly release the tensioner—do not let it snap back.
4. Install the new belt: Route the new belt following the path described above. Leave the alternator or water pump for last.
5. Apply tension: Compress the tensioner again, slip the belt over the final pulley, and carefully release the tensioner.
6. Verify: Check every pulley to ensure the ribs of the belt are seated perfectly into the grooves of the pulleys. Start the engine and observe the belt for any wobbling.

Replacement interval

For the 2015 Toyota Highlander, the serpentine belt should be visually inspected every 15,000 miles or 18 months. The typical replacement interval is between 60,000 and 90,000 miles. EPDM belts (like the OEM and modern aftermarket ones) do not crack as obviously as older neoprene belts; instead, the ribs wear down like tire tread. A belt wear gauge is the best tool to check rib depth.

Signs of a failing belt or tensioner

Keep an ear and eye out for these common warning signs:

• Squealing or Chirping: Especially on cold startups or when the A/C compressor engages. This indicates a loose, worn, or glazed belt.
• Visible Wear: Missing chunks, fraying edges, or exposed cords mean the belt needs immediate replacement.
• Tensioner Bounce or Rattle: If you watch the tensioner while the engine is running and see it jumping erratically or hear a metallic rattling, the internal spring or dampener is failing.
• Bearing Whine: A continuous whining or grinding noise often points to a failing bearing in one of the idler pulleys or the tensioner pulley.
• Overheating or Battery Light: If the belt snaps, you will lose the alternator and water pump, leading to immediate overheating and battery discharge. Pull over immediately if this happens.

Replacing the belt and tensioner is excellent preventative maintenance. If you don't feel comfortable tackling this in your driveway, you don't have to put it off. Find a trusted shop on Repairius.