A lit-up diesel particulate filter warning light isn’t as serious as some other warning lights – but that doesn't mean you should ignore it. It lets you know there is an issue with your vehicle's DPF, usually indicating that it's blocked or struggling to regenerate.
If you don't solve the problem and clear the warning light, your diesel vehicle may enter 'limp home mode' which can severely limit your performance and lead to more serious problems.
Read on and find out what an illuminated DPF warning light means, what you should do when it comes on, and how to clear the DPF light.
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What Does the DPF Warning Light Mean?
The DPF warning light is there to let you know that there is an issue with your vehicle’s diesel particulate filter.
Your car’s diesel particulate filter is responsible for trapping and removing harmful particulate matter from the exhaust gases.
Usually, the light comes on if the diesel particulate filter is becoming blocked or is struggling to regenerate.
Active regeneration is automatically triggered by your car’s electronic control unit (ECU) when your car has been in motion long enough to reach a certain temperature.
Passive regeneration can be triggered when you drive at around 40mph on the motorway for 20 minutes or more.
The light should go out once the regen process is complete, but you must give the DPF enough time to reach its higher temperature for the process to work.
If the light stays on even after trying to trigger passive regeneration - or it keeps coming on - you must take your car to a professional mechanic so they can force DPF regeneration, and clean or replace the DPF if needed.
The symbol for your DPF warning light usually looks like a little box with holes in it.
There are two types of DPF warning light which you may see on your dashboard.
Flashing DPF Light
If your DPF light flashes, this means that the level of soot is almost at full capacity.
When your DPF is 70% full of soot, your car will enter ‘limp home’ mode, meaning vehicle performance will be restricted.
Solid DPF Light
This yellow or amber DPF light shines to indicate you are approaching maximum soot levels.
This means that your vehicle needs to go through the regeneration process to unblock your DPF.
By the time your DPF is 90% full of soot, there will be little you can do to prevent the need for a full-on DPF replacement.
What Can Cause the DPF Light to Come On?
Any of the following could be causing the DPF light to come on:
- Faulty regeneration system
- Faulty sensors
- Low quality fuel
One of the most common reasons why the DPF light might be coming on is if you are regularly taking the vehicle only for short drives at lower speeds.
Driving like this can cause your DPF to become blocked, as it won’t have enough time to regenerate fully.
How Do You Clear a DPF Warning Light?
The process of clearing the DPF warning light can vary depending on what is causing it to stay on.
You can try to clear the DPF warning light by driving on the motorway for 15 minutes or more at a speed of at least 40mph.
You can visit a garage if you are concerned about your car’s DPF light staying on.
A mechanic will be able to diagnose the underlying issue causing the DPF blockage for you.
If the DPF is heavily blocked, then a professional DPF clean or replacement may be necessary.
Should I Be Worried About This Light?
Whether or not you should worry about your car’s DPF warning light all depends on the reason why the light has come on.
It could be the case that your DPF just requires regeneration, or it could require professional attention.
If you tend to drive short distances or in stop-and-go traffic, then your car’s diesel particulate filter may be more prone to blockages.
Older vehicles and those with high mileage are also more likely to encounter DPF problems due to engine wear and tear.
If the warning light stays on even after you attempt regeneration, you should book an appointment at a professional garage so that they can advise you further.
Can I Drive with the DPF Warning Light On?
Once the DPF light is illuminated, this is a sign that your DPF filter is nearly fully blocked.
Though your vehicle won’t stop running when the light turns on, keeping driving can cause further issues with reduced vehicle performance, decreased fuel efficiency or even engine damage.
If you keep driving with the DPF light on, this can result in reduced fuel efficiency, loss of engine power and the need for more costly repairs.
The ECU will put your vehicle into 'limp home' mode if you keep driving, meaning that if the ignition is turned off the vehicle may not restart, so you won't be able to drive for long with the DPF light on.
Will a Blocked DPF Clean Itself?
If your DPF has become heavily blocked, then driving at speed to try and trigger regeneration won’t be enough.
You will have to take the vehicle to a garage or dealer so that they can do a manual – or ‘forced’ - regeneration.
It may even be the case that the filter needs to be replaced altogether, which can cost upwards of £1,000 plus labour.
How Can I Take Care of My DPF?
There is usually only a short time between the DPF light becoming partly blocked and it requiring forced regen.
That’s why is essential that you regularly take your vehicle for drives of at least 20 minutes at a speed of at least 40mph on the motorway.
You should also opt for high quality fuel to minimise the risk of particulate build up in the diesel particulate filter.
Regular car servicing is another must, as your oil and filters need to be changed as per the manufacturer's guidelines.
Be sure to book a DPF clean every 6 to 9 months to keep your DPF working well.
When you book in for a DPF cleaning service through BookMyGarage, this can cost you as little as £99.
This includes a full inspection, diagnosis and flush, all performed by highly-qualified mechanics.
