What Happens If You Run Out of DEF? Discover the Ram’s Power-Packed Consequences!

What Happens If You Run Out of DEF on Your Dodge Ram

Many contemporary diesel vehicles, including the Dodge Ram, are equipped with a selective catalytic reduction (SCR) system that requires the use of Diesel Exhaust Fluid (DEF), also known as AdBlue, for emissions control.

DEF is a solution made up of urea and deionized water that is injected into the exhaust stream. It helps to reduce harmful nitrogen oxide (NOx) emissions by converting them into harmless nitrogen and water vapor. However, if you run out of DEF on your Dodge Ram, here’s what you can expect:

1. Reduced Engine Performance

When your Dodge Ram runs out of DEF, its engine power will be limited. The vehicle’s onboard computer will activate a speed limiter, typically capping your maximum speed at around five miles per hour. This restriction is in place to encourage you to refill the DEF tank as soon as possible to ensure emissions compliance.

2. Engine Warning Lights and Alerts

Running out of DEF triggers various warning lights and alerts on your vehicle’s dashboard. You’ll likely see a DEF warning light, a check engine light, and a message indicating that the vehicle’s speed has been limited. Sometimes, these alerts may also include audio warnings or prompts.

3. Inability to Start the Engine

In some cases, running out of DEF can prevent your Dodge Ram from starting altogether. Modern diesel vehicles with SCR systems often incorporate start prevention mechanisms to ensure that the required emission standards are met. The engine may refuse to start until the DEF tank is refilled.

4. Vehicle Non-Compliance

Running out of DEF not only leads to reduced engine performance but also puts your vehicle in non-compliance with emission regulations. In some regions, driving a diesel vehicle without proper emissions control can lead to penalties, fines, or even surpassing emission limits set by the authorities.

5. Costly Repairs

If you repeatedly run out of DEF or ignore the warning lights, it can cause long-term damage to your vehicle’s SCR system. Dealing with repairs or replacement of these components can be expensive, potentially costing you hundreds or even thousands of dollars.

Frequently Asked Questions Of What Happens If You Run Out Of Def? Discover The Ram’s Power-packed Consequences!

What Happens If You Run Out Of Def Dodge Ram?

Running out of DEF (diesel exhaust fluid) in your Dodge Ram can result in your vehicle entering a limited performance mode, reducing its power and capabilities.

How Does Running Out Of Def Affect My Dodge Ram?

Running out of DEF can trigger a series of warning indicators on your Dodge Ram’s dashboard and may even cause your vehicle to enter a limp mode, restricting it to lower speeds.

Can I Drive My Dodge Ram Without Def?

Technically, it is possible to drive your Dodge Ram without DEF, but it is strongly advised against as it can lead to reduced engine power, increased emissions, and potential damage to the exhaust system.

What Are The Signs That My Dodge Ram Is Running Out Of Def?

Warning indicators such as a DEF level warning light, loss of power, or a message on your Dodge Ram’s display system typically indicate that your vehicle is running low on DEF.


Running out of DEF on your Dodge Ram can have significant consequences, including reduced engine performance, engine warning lights, an inability to start the engine, non-compliance with emission regulations, and potential costly repairs. It’s crucial to regularly monitor your DEF levels and refill the tank to prevent these issues from occurring. If you find yourself running low on DEF, it’s best to address it promptly to maintain your vehicle’s performance and ensure compliance with environmental regulations.

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