DEF light

DEF Warning Car Dashboard Light

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DEF Warning Car Dashboard Light Indicator

The Diesel Exhaust Fluid (DEF) warning light on a car dashboard indicates that the DEF reservoir is low on fluid. DEF is a solution used in diesel vehicles to help reduce environmental damage by minimizing harmful nitrogen oxide (NOx) emissions. The DEF light serves as a warning to the driver that the DEF tank is nearing empty. This issue is more significant for truck drivers than for drivers of passenger cars.

DEF Warning Light Stages

  1. Amber Light: If the DEF level drops below 2.5%, the indicator will become solid amber.
  2. Red Light: If you continue to drive without refilling the DEF tank, the light will eventually turn solid red, signaling that you have run out of DEF. Ignoring this red light can lead to your vehicle’s speed being limited to 5 mph until the DEF tank is refilled.

Consequences of Ignoring the DEF Warning Light

Ignoring the DEF warning light can result in:

  • Loss of power
  • Damage to the DEF system
  • Expensive repairs
  • Unwanted downtime

Proactive Maintenance

To avoid problems associated with the DEF warning light, drivers should:

  • Regularly check and refill the DEF tank
  • Be cautious not to contaminate the DEF tank with diesel fuel or other substances
  • Familiarize themselves with the DEF refilling process

What Happens If You Don’t Pay Attention to the DEF Warning Light?

If you ignore the DEF warning light, your car’s computer will detect the low DEF level and put your vehicle in reduced power mode, limiting emissions and performance. In some cases, the car may refuse to start unless the DEF tank is replenished.

How to Prevent the DEF Warning Light from Coming On

To prevent the DEF warning light from coming on:

  • Regularly check and refill the DEF tank
  • Locate the DEF filling port near the diesel fuel filler hole in most trucks, or consult your owner’s manual for its location in other diesel vehicles
  • Learn about the DEF refilling procedure to avoid contamination

Where to Get DEF Refills

You can purchase DEF at dealerships, auto parts stores, and most car maintenance shops.