The exhaust particulate filter warning light is a light that will show up on the dashboard of a diesel car when soot from the exhaust has reached high levels. Diesel engine exhausts are fitted with a particulate filter that is designed to control high emission levels. It catches the larger particles of soot coming from the exhaust. Here is everything you need to know if you see your exhaust particulate filter warning light turn on.
Why is My Exhaust Particulate Filter Warning Light On?
The exhaust filter on your diesel car will clog up over time, which can lead to restricted airflow and cause your car’s performance to deteriorate. Car manufacturers have come up with several ways to regenerate the filter to prevent this. Regeneration occurs when the exhaust temperature is raised high enough to burn away the soot particles, turning them to ash. The exhaust particulate warning light will usually show when the filter needs to be regenerated.
What is the Exhaust Particulate Filter Warning Light?
When you are driving your car, its computer is always monitoring the levels of soot within the filter to determine when the regeneration process is needed. However, the car needs to reach high speeds for the exhaust to be hot enough to burn the soot. If you don’t travel on the motorway very often, the exhaust may never get hot enough, and your warning light will show. If you see the warning light on your dashboard, you will usually be able to fix the problem by taking your car to a higher-speed road such as a motorway and driving at a higher speed – at least 40MPH for ten to fifteen minutes.
What Does it Mean When the Exhaust Particulate Filter Warning Light is Flashing?
A flashing light may occur when the exhaust filter needs to be regenerated. This will usually depend on the model of the car. If you see the light flashing, you will need to take your car to a higher-speed road where you should drive it for ten to fifteen minutes at a higher speed to burn the soot away from the filter.
How Does the Exhaust Particulate Filter Warning Light Work?
This warning light appears to let drivers of diesel cars know that there are soot particles gathering in the exhaust filter. It is an indication that you need to take your car to a higher-speed road and drive at high enough speeds to warm up the exhaust to a temperature that can successfully regenerate the filter. When this is done successfully, the warning light should be switched off.
What are the Common Reasons the Exhaust Particulate Filter Warning Light Will Come On?
The one main reason for the exhaust particulate filter warning light turning on is that the filter needs to be regenerated. This involves burning the soot in the filter to ash. This is achieved by raising the temperature, which is done when your car is moving at a high speed.
The light might also be on and could be accompanied by further warning lights if your car is in limp mode. This happens if the soot builds up to larger levels and is a last attempt to save the filter. In limp mode, the top speeds of your car will be limited. You may need to have a forced regeneration program carried out by a professional in order to fix this issue.
Is it Dangerous to Drive with the Exhaust Particulate Filter Warning Light On?
It is not dangerous to drive with this warning light on. However, you should try to drive your car at a higher speed as soon as possible. If you see this light when you are driving, take your car to the nearest motorway or an A road that has a speed limit of 40MPH or more so that you can drive for a certain amount of time at a certain engine rev level to regenerate the filter.
If you ignore the warning light and the filter is not regenerated, the car will go into limp mode to limit the amount of soot passing through the filter. A forced regeneration program will be needed to clear the filter and take your car out of limp mode. If limp mode is ignored and the filter is not regenerated, the filter might need to be replaced. Driving your car without a particulate filter, or removing the filter, is illegal and should not be attempted.
How Much Does It Cost to Fix the Exhaust Particulate Filter Warning Light?
The cost will vary depending on the severity of the problem. If the filter needs to be regenerated, this is often a quick and easy fix that is only going to cost you the amount of fuel that you use. You will need to take your car to a road where you can safely and legally travel at a higher speed. At higher speeds, the exhaust will reach a temperature where it can regenerate the filter by burning the soot away and turning it to ash.
However, if you ignore the warning light and the car goes into limp mode, this can be a more expensive issue to deal with. A forced regeneration program will need to be run by a mechanic to clear out the filter of soot and disable the limp mode. This will cost an average of £100.
The most expensive fix is if the particulate filter needs replacing. These cost between £1000 and £3500 and may even set you back more than your car is worth if you have an older diesel car.
Will My Car Fail its MOT if the Exhaust Particulate Filter Warning Light is On?
Most warning lights will fail the MOT if they are consistently shown on the dashboard throughout the test. A particulate filter check is a standard part of the MOT for any diesel vehicle. Problems with the particulate filter will often lead to an MOT fail, as will the car is in limp mode throughout the test. If the particulate filter is missing or has been removed, this will be an automatic MOT failure.
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