The 2022 and newer Toyota Tundra i-Force MAX Hybrid powertrain starts with the very same 389 horsepower Otto Cycle 3.4-liter twin turbocharged all-aluminum V6 engine found in the non-hybrid Tundra pickups. With 479 pound-feet of torque, the engine features dual overhead cams with variable timing, both direct and port fuel injection and air-to-water inter-cooling for its boosted air charge.

Setting the i-FORCE MAX Hybrid apart is a 48 horsepower electric motor/generator sandwiched between the V6 and its 10-speed automatic transmission which is powered by a 1.87 kWh Nickel-Metal Hydride (Ni-MH) battery pack.

Together this parallel hybrid system produces a total system 437 horsepower and 583 pound-feet of torque burning baseline 87-octane fuel. In the 2024 Tundra Limited 4×4 we tested it’s rated by the EPA at 19 mpg city, 22 mpg highway and 20 mpg combined.

A look around the engine compartment also shows a few key differences starting with the hybrid power converter and control unit mounted high against the firewall at the passenger side where you might expect to find a 12V battery. Instead, the 12V battery is located under the rear seat at the driver side adjacent to the high-voltage hybrid battery assembly which itself has a rating of about 650 volts.

Also unique to the hybrid is an electrically driven AC compressor instead of a belt-driven unit which allows the cool air to continue flowing even when the gasoline engine is not running. All together with its components the Tundra hybrid weighs on average about 600 pounds more than a non-hybrid version.

Following the airflow there are actually two separate air-filter boxes and intake systems, one on each side. For simplicity we’ll follow one which routes the intake charge to one of the two turbochargers and from there up to the air-to-water inter-cooler mounted high atop the engine.

Traveling through the inter-cooler, the air then passes through a throttle body at the rear and then down under into the main intake manifold which is mostly hidden from view as is the majority of the duel fuel injection system Toyota calls D4S.

After combustion takes place the spent exhaust then exits at the bottom side of each cylinder bank and into the aforementioned turbochargers which are hard to actually see and then directly into the exhast system.

Though packaging is obviously quite tight, DIY maintenance for routine service is relatively straight forward. There are three coolant reservoirs. The first at the passenger side firewall is for the hybrid control system. Next are the two reservoirs located at the top front of engine bay. The one on the left is for the air-to-water inter-cooler and the one on the right is for the main engine cooling system.

The engine oil filler cap is found at the top left side of the engine and the oil dipstick is located at the top right. Both can easily be accessed and used with or without the engine sound cover in place, an item that easily snaps on and off. The oil filter is mounted down low and must be accessed from underneath.

Both air-filters are easily accessed for checking and changing by simply popping a couple of clips, no tools are required. The main consumer grade fuse box is located at the passenger side just behind the air filter with a fuse removal tool found inside.

The windshield washer fluid cap can be found at the driver side front of the engine bay sitting atop a long vertical tube that routes to the tank which itself is mounted down low. Brake fluid is checked and topped off at the driver side firewall location as expected. The reservoir sites atop an electronically controlled brake pump and is immediately adjacent to the ABS control unit.

Changing spark plugs on this engine appears to be an involved process as the majority of them are hidden beneath several other components which will need to be removed out of the way first. This is a job best reserved for experienced and patient hands with a good collection of tools.

A couple of important notes when working around the engine bay, start with the bright orange cables which connect the hybrid battery to the various components. Always avoid these as they carry up to 650 volts and are not typically user serviceable anyway.

The main engine cooling fan is belt-driven by the engine in a more traditional set up and is not going to be a hazard to your hands unless the engine is running. There are however additional auxiliary electric cooling fans at the front of the radiator package which can power up at any time though they are mounted in a place where it’s unlikely your hands will be roaming.