Is it safe to drive with the DEF indicator on?
Auto repair

Is it safe to drive with the DEF indicator on?

09.11.2022 /

A tractor trailer on the side of the road ideally means the driver has stopped to take a nap. Of course, this can also mean breakage. One alarming scenario is when the DEF indicator lights up. DEF…

A tractor trailer on the side of the road ideally means the driver has stopped to take a nap. Of course, this can also mean breakage. One alarming scenario is when the DEF indicator lights up.

The DEF (Diesel Exhaust Fluid) indicator is a driver warning system that tells the driver when the DEF tank is nearly empty. This affects truck drivers more than car drivers. DEF is essentially a blend that is added to a car's engine to reduce environmental damage by blending with diesel fuel. The DEF light comes on when it's time to add fluid, and as far as whether it's safe to drive with the light on, yes it is. But you don't have to. If you do, you may be in trouble.

Here are some things to know about driving with the DEF indicator on:

  • Before your DEF tank is empty, you will see a warning on the dashboard in the form of a DEF indicator. If your DEF drops below 2.5%, the light will be solid yellow. If you choose to ignore this, the moment you run out of DEF, the indicator will turn red.

  • It gets worse. If you ignore the solid red light, your vehicle speed will be reduced to a snail's speed of 5 miles per hour until you fill up the DEF tank.

  • The DEF warning light may also indicate contaminated fuel. The effect will be the same. This type of contamination most often occurs when someone accidentally pours diesel into a DEF tank.

Most often, loss of DEF fluid is due to driver error. Drivers sometimes forget to check the DEF fluid when they check the fuel level. Not only does this result in a loss of power, but it can also damage the DEF system itself. Repairs can be very costly and can, of course, result in unwanted downtime for the driver.

The solution, obviously, is proactive maintenance. Drivers need to be vigilant when it comes to DEF so they don't waste time, damage their vehicles, and get into big trouble with their employer. Ignoring the DEF indicator is never a good idea, so if it comes on the driver should stop and refuel their DEF immediately.

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