What Your Vehicle’s Diesel Particulate Warning Light is Trying to Tell You


The dreaded warning light. When a warning light turns on, there is always the temptation to ignore it. The experts at Ace Supply explain why ignoring it is never a good idea.

When the diesel particulate filter warning light turns on it means that the soot level from the diesel exhaust is high and your vehicle is likely to go into limp mode.

Today’s diesel engines are fitted with a particulate filter within the exhaust that is designed to catch larger particles of soot that come from the diesel exhaust. Of course, as is the case with all filters, there will come a time when it will clog. This will cause airflow to be restricted and the performance of the particulate filter to be reduced.

While the warning light signals an issue with the particulate filter, it doesn’t mean that your vehicle is about to give out, leaving you stranded on the side of the road. That is because there are a few ways that the filter can be regenerated. This is accomplished by raising the temperature in the exhaust to a level which burns the soot, reducing it to ash. This is referred to as active regeneration.

Another type of regeneration is called passive regeneration. This allows an engine to burn off extra fuel even when it doesn’t reach high speeds on a regular basis. Passive regeneration allows the temperature to get high enough, at lower speeds, to burn the soot off. These two types of regeneration work together to keep the particulate filter from becoming clogged.

When the soot level reaches a certain threshold, typically a little less than 50 percent, the engine will work to reduce the level of soot. At this point the warning light will come on, letting you know that there is an issue. While there is no reason to panic, it is important to take the vehicle onto the highway and drive it at speeds higher than 40 mph to raise the temperature and regenerate the filter. This should result in the warning light turning off.

The worst thing you can do is to ignore the warning light. Doing so will mean soot will continue to build up, ultimately leading to the vehicle’s computer to go into limp mode to prevent more damage. Limp mode limits a vehicle’s speed in an effort to reduce the amount of soot being sent through the filter. If your vehicle goes into limp mode, you may be able to save the filter, but it will require a professional to do it. Therefore, it is in your best interest to never let things get to this point. If you do, you will be looking at a costly repair or replacement.

As a CrownSource customer, you have access to deep discounts on the products you need – like Ace Supply aftermarket parts including Diesel Particulate Filters to keep your fleet running smoothly. Login to our eProcurement Platform, CrownConnect, to see all our aftermarket parts and over three million other products sourced especially for the transportation industry. Not a customer? Schedule a demo now.

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