Where Is The DEF Located On The Isuzu Reach? (With Pictures)

Isuzu reach is a medium-duty walk-through van developed in partnership with Utilimaster. It was launched in 2011 and has since become the van of choice for many companies, including FedEx and UPS. As a commercial van, the Isuzu reach ticks several boxes, making it a delight to business owners. It has a timeless design that still looks modern 11 years after it was first introduced. Its 540 or 639 cubic feet of storage is enough for conveying small packages and containers. 

With 27 inches of headroom, the driver has more than enough space to maneuver, and safety features like the thread-grip carbide entry steps, yellow cab entry handles, and ergonomic dashboard controls point to the fact that its designers spent a good amount of time thinking of ways to improve its safety. Evidently, the Isuzu reach has few contenders when it comes down to design, but they didn’t stop there. 

Combining good aerodynamics with a lightweight body, the 3-liter diesel engine can run smoothly on less fuel (than most other minivans), and a top of class Selective Catalytic Reduction (SCR) technology using Diesel Exhaust Fluid ensures that pollution is kept to the bare minimum. There are so many points to spotlight, but our focus in this article is on the engine, specifically the Diesel Exhaust Fluid (DEF). Before we get down to the crux of the matter, which is the location of the DEF, let’s talk about the Engine. 

What is DEF?

DEF is a chemical solution of urea and water that acts as a catalyst in the selective catalytic system to reduce harmful NOx gases present in exhaust fumes before they are released into the atmosphere. DEF is not mixed with the fuel; rather, it is stored in a different tank from where a specific quantity is injected into the exhaust stream.

Without the DEF, truck manufacturers would have to step down the trucks’ performance to mitigate the negative environmental impact. So the DEF allows truck manufacturers to meet the EPA guidelines without compromising the engine’s performance or fuel economy. It became mandatory for all trucks produced after 2010 to meet new emission standards imposed by the EPA. This means that just like the diesel that runs the truck, drivers have to ensure their truck never runs out of DEF. 

Where is the DEF tank located on the Isuzu Reach?

The location of the DEF tank varies with each manufacturer. The Isuzu Reach is one of the earliest adopters of the Selective Catalytic Reduction (SCR) system. While you can barely see most components of the SCR, drivers will regularly use the DEF tank when they want to refill the DEF.

On the Isuzu Reach, the DEF tank is located on the left side of the van. This is the common location of the DEF tank for most Isuzu trucks. However, on the Reach, the DEF tank is further down the cargo body, just before the tire.

isuzu reach def tank

The DEF tank can easily be recognized by its blue filler cap, which is intended to differentiate it from the diesel tank, which usually has a black filler cap. You should also see a label saying “DEF FILL ONLY” right above the tank’s location. 

Isuzu Reach Engine Overview

Here is a short overview of the Isuzu Reach engine to better understand why DEF was introduced and how it helps.

Powering the Reach is a 4JJ1-TC turbocharged four-cylinder engine with a displacement of 3 liters and capable of generating up to 150 hp and 282 ft-lb of torque. The engine is optimized to deliver high performance while minimizing fuel consumption.

A closer look at the engine’s inner workings, it immediately becomes obvious that Isuzu engineers had hit their mark. The dual overhead camshafts help to reduce engine friction while allowing for better air intake since each cylinder can have up to 4 valves, two valves each per camshaft for intake and exhaust. 

This design allows the engine to generate more power (since air intake is higher) and also wastes less power pushing out the exhaust gases. The cylinder head is made of cast aluminum which is both durable and lightweight.

For transmission, the Isuzu Reach uses an Aisin A460 6-Speed auto with a double overdrive that reduces engine wear, lowers engine noise, and improves fuel economy. It is regular maintenance, like an oil change, only becomes necessary after about 10,000 miles. A B-10 rating means that about 90% of the engine will still operate normally after 310,000 miles. 

By all standards, these specs are impressive, but like every other internal combustion engine, it contributes its fair share to global warming. Statistically, delivery trucks like the Isuzu Reach generate about 19.7 tons of carbon dioxide, half of all Nitrogen Oxide (NOx) emissions and nearly 60% of fine particles.

NOx and fine particles are by-products of diesel engines like the 4JJ1-TC in the Isuzu Reach. To cut down on these emissions, the Isuzu Reach (like most other diesel-powered trucks) makes use of a Selective Catalytic Reduction (SCR) technology that uses Diesel Exhaust Fluid (DEF) to reduce Nox gases to elemental Nitrogen and water. 

Does Isuzu Reach have a DEF level gauge?

Yes. The DEF level gauge is located on the MID or dashboard. The gauge level looks like a battery icon and is always visible on the dashboard once the van is turned on. At the top of the gauge is the letter “F” and at the bottom of the gauge is the letter “E,” representing Full and Empty, respectively.

Isuzu reach def gauge

If the DEF tank is full, the DEF level gauge will display four green bars. As the DEF level drops, the number of bars will also drop accordingly. If the DEF level gets too low and you haven’t refilled it, the system will alert you to do so. 

What happens if the DEF tank is empty?

While the DEF is not used up as quickly as the diesel, it eventually gets low and needs to be refilled. Failure to do so will drastically reduce your vehicle’s performance. How far the engine is throttled depends on how much DEF you have left.

isuzu reach low def level

First of all, you’ll see the reduced engine power indicator light followed shortly by the “Refill DEF” message and a chime. If you keep driving for a while despite these warning signs, the engine will be throttled to ensure that the emission is well within the stipulated EPA guidelines. This will be done in stages. First, the speed will be limited to 55 MPH and then 35 MPH, and finally, after you’ve run out of DEF, the engine speed will be limited to 5 MPH. At this speed, the van’s emissions are at a tolerable level. 

How often does a DEF tank need to be filled? 

The SCR system uses about 2 to 3 gallons of DEF for every 100 gallons of diesel. The actual amount depends on the operational condition of the vehicle, like the load rating and road conditions. 

Now the Isuzu Reach has a diesel tank with a capacity of 25 gallons which needs about 0.5 gallons of DEF (at 2 gallons DEF per 100 gallons of diesel). At this rate, you will need to refill a 5-gallon DEF tank after filling your diesel tank about 10 times.

But you don’t need to perform all these complicated calculations because the Isuzu Reach identifies when the DEF needs to be refilled. Usually, an alert will pop up on the dashboard telling you to Refill Def when the gauge has about one green bar left (see reference photo).

How many miles will 5 gallons of DEF last?

Isuzu Reach has a reputation for good fuel economy. According to the manufacturers, the Isuzu Reach is 35% more fuel efficient than the average truck. We would have preferred precise numerical values to work with instead of percentages. However, we do know that DEF consumption is directly proportional to fuel consumption.

So if you have better fuel economy, the DEF consumption will likely be much less than the average. The Isuzu NPR may not be like the Reach, but they are estimated to average 16 MPG. Let’s assume the Reach can attain the same level of fuel economy or better. Then for 16 MPG, you’d go about 800 miles with a gallon of DEF (at 2 gallons of DEF per 100 gallons of diesel). Now 5 gallons of DEF will go for about 4000 miles. 

Is it better to keep the DEF tank full?

Yes. It is always good to top off the DEF tank frequently, so it doesn’t get too low or run out. If this happens at a place and time when you can’t get DEF, then you will be forced to drive at a lower speed until you refill the DEF. 

Is it safe to drive my Isuzu Reach with an empty DEF tank?

There is no harm to your vehicle if you drive with an empty DEF tank. However, you’d be harming the environment, and to stop that from happening, you’ll be forced to drive at very low speeds until the DEF is refilled. 


Isuzu Reach has a timeless and ergonomic design, a superb engine, and several safety features that have earned it many accolades. Although it would likely not be the first to come to mind, the SCR system is among many of the most crucial components of this van. Within the SCR system is yet another important component, the DEF. In this article, I have discussed the DEF, its location, and why it matters.