Reset Your Hino 268 DEF Light: The Step-by-Step Guide for Drivers

If you're a driver of a Hino 268 or similar medium-duty truck, seeing the DEF (Diesel Exhaust Fluid) warning light illuminate on your dashboard can be stressful. This light often triggers escalating warnings that can ultimately lead to your truck's speed being severely limited. While the light can indicate a serious problem, it is often triggered by a simple issue you can fix yourself. This guide will walk you through the steps a driver can take to reset the light and get back on the road.

The Short Answer: Your First Two Steps

In over 90% of cases, a DEF/DPF warning light can be fixed by doing one of two things:

Refill the DEF Tank: The most common cause is a low DEF fluid level. The tank has a blue cap.
Perform a Manual DPF "Regen": If the DEF tank is full, the truck's diesel particulate filter (DPF) needs to be cleaned. This is done by parking safely and pressing the DPF/Regen button on the dash.

⚠️ IMPORTANT: Do Not Ignore These Lights!

The DEF/DPF warning system is designed to force you to take action. If you ignore the initial warnings, the truck's computer will begin a countdown that will eventually derate the engine's power and limit your speed, often to as low as 5 mph (8 km/h). This is a required emissions and safety feature, not a malfunction. You must address the warning promptly.

Step-by-Step Guide to Resetting the Light

Follow these steps in order. Most of the time, Step 1 is all you will need.

💧 Step 1: Check and Refill the DEF Tank

This is the simplest and most common fix. The DEF light is often just a low fluid warning.

Safely park the truck on level ground and turn off the engine.
Locate the DEF tank. It's usually on the driver's side, next to the diesel fuel tank, and has a smaller, bright blue cap .
Check the level via the dashboard gauge or a sight glass on the tank.
Refill the tank. Use only new, high-quality DEF from a sealed container, available at any truck stop or auto parts store. Fill the tank until it is nearly full, but do not overfill.
Start the truck. After refilling, start the engine. In most cases, the sensors will detect the full tank, and the DEF warning light will turn off automatically after a few moments. If it stays on, proceed to Step 2.

🔥 Step 2: Perform a Manual DPF Regeneration ("Regen")

If the light is still on, the truck's Diesel Particulate Filter (DPF) is full of soot and needs to be cleaned. The truck usually does this automatically at highway speeds, but lots of city driving requires a manual "regen."

Ensure Conditions are Safe: This is critical. The exhaust gets extremely hot during a regen (over 1,000°F / 540°C). You MUST park the truck outdoors, away from any flammable materials (buildings, dry grass, fuel sources) or people.
Warm Up the Engine: The engine needs to be at normal operating temperature. Let it idle for 5-10 minutes if it's cold.
Press the DPF/Regen Button: On the Hino 268 dashboard, press and hold the button with a DPF symbol (a rectangle with dots inside) for a few seconds. The engine RPMs will increase, and an indicator light will show the regen process has started.
Wait. Do Not Interrupt. A manual regen can take 20 to 60 minutes . The engine will run at a high idle. Do not turn off the engine or drive the truck.
Process Complete: Once finished, the engine RPMs will return to normal, and the DPF indicator light will turn off. The main warning light on your dash should now also be off.

When These Steps Don't Work: Time to Call for Service

If you have refilled the DEF tank and successfully completed a manual regen, but the warning lights remain on or come back on quickly, you have a more serious problem that requires a mechanic. Do not continue to drive the truck. The issue could be:

A failed DEF injector, pump, or sensor
A clogged DPF filter that needs professional cleaning or replacement
Poor quality or contaminated DEF fluid

In these cases, the truck needs to be connected to a diagnostic computer to identify the specific fault code. Continuing to drive will only lead to the truck being derated, potentially leaving you stranded.

Frequently Asked Questions

Is it safe to drive with the DEF light on?

You can drive for a short period when the light first comes on, but you should address it as soon as possible. The system will give you a series of escalating warnings before it derates the engine. The longer you wait, the more likely you are to be forced into "limp mode" with severely reduced speed.

Why does my truck need a manual regen so often?

Frequent requests for manual regens are almost always caused by a lot of low-speed, stop-and-go driving. The engine isn't getting hot enough or running at a high enough RPM for a long enough period to perform the automatic "passive" regen. This is common for trucks used in local delivery or vocational applications.

What happens if I interrupt a regen?

If you interrupt the process, the DPF will not be fully cleaned, and the warning light will likely come back on soon. You will then have to start the entire process over again. It's best to let it complete fully.

Conclusion: A Driver's First Line of Defense

The Hino 268's DEF/DPF system is a critical part of its modern emissions controls. While its warning lights can be intimidating, the solution is often simple. By first checking the DEF fluid level and then, if necessary, safely performing a manual DPF regeneration, drivers can handle the most common issues themselves and avoid costly downtime and service calls. Knowing these two simple procedures is a crucial piece of knowledge for any Hino operator.

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