DPF light on, limp mode, or a diesel that has lost its power. We find out how full the filter is and why it blocked, then regenerate, clean or replace it.
A clean filter on a car with a dead sensor just blocks again. So we fix the cause as well as the filter, and you get a fixed price before any work starts.
Find the cause first
Then fix the filter. Never the other way round.
How full it is, read on the scanner
Why it blocked, not just that it did
Fixed price before work starts
The honest bit
The diesel particulate filter sits in the exhaust and catches the soot a diesel makes. To stop itself filling up, it has to get hot enough to burn that soot off, which is called regeneration. That takes heat and time: a decent run at a steady speed.
Short, cold trips never give it either, which is why so many DPF lights come on in winter. Often a proper run on the M5 sorts it. But when a filter keeps blocking even with good runs, the filter is rarely the real problem. A sensor has failed, an EGR valve is sticking or the engine is never getting properly hot.
That is the bit that gets skipped. A filter gets cleaned or replaced, the cause is left in, and a few months later the light is back and you are paying again.
If your DPF light has just come on, today is the cheapest it will ever be to sort. Leave it until limp mode and it costs more.
Symptoms decoded
None of these is a diagnosis on its own, and anyone selling you a new filter over the phone is guessing. But they do tell you how urgent it is.
The amber box with dots in it. The filter is filling with soot faster than the car can burn it off. On its own it is a warning, not a breakdown, and on most cars around twenty minutes at a steady speed on a dual carriageway will clear it.
The filter has loaded so far that the engine management is protecting the engine. Another run will not fix it now. It needs reading to see how full the filter is, and that decides whether a regeneration will work or it needs cleaning or replacing.
This is the one that matters. If the car gets proper runs and still blocks, something is stopping the filter regenerating: a sensor, a sticking EGR valve, an injector, a thermostat stuck open. Clean the filter without fixing that and it blocks again.
The engine management has logged a fault, which may be the DPF itself or the thing causing it, such as a failed exhaust temperature or pressure sensor. The stored codes are the most useful evidence there is, so get it scanned rather than waiting for it to clear.
Often this is the car in the middle of a regeneration, and on its own it is normal. If you keep switching off before it finishes, though, the filter never empties. If it is happening on nearly every trip, the filter is asking for a proper run.
A diesel with a working DPF should not smoke. Visible smoke points to a damaged or bypassed filter or an engine fault upstream, and since 2018 any visible smoke from a DPF diesel is a major fault at the MOT.
The fix
It depends on how full the filter is, what it is full of, and whether it is damaged. That is read on the scanner and, where needed, by looking at the filter itself. We tell you which one yours needs, and why, before anything is done.
1
£250
With diagnostic equipment the car is held at a fast idle while the system raises the exhaust temperature and burns the soot off. It suits a filter that is heavily loaded but not packed solid. The price includes an oil and filter change, because the extra fuel a regeneration burns ends up diluting the engine oil.
2
Quoted after diagnosis
A clean with the filter still fitted, for a filter too full to regenerate but still sound. Quicker than taking it off, and not right for every filter.
3
From £299
We strip the filter off the car here, and a specialist cleaner just round the corner cleans it properly, which also clears the ash no regeneration can burn. Then we refit it. The route the A200 below went down.
4
Quoted after diagnosis
For a filter that is cracked, melted or too far gone to clean. A new filter, or a professionally cleaned one where that suits the car and the budget.
Whichever it is, the fault that blocked the filter gets fixed too. Otherwise you pay twice.
If the car gets proper runs and the light still keeps coming back, one of these is usually behind it.
A DPF light can come on for a number of reasons, so diagnostics always comes first and is charged on its own. It is what tells us whether a regeneration will work, whether the filter needs cleaning, and what blocked it.
Then you get a fixed price before any work begins. No surprises, and no phone call halfway through that changes the number.
12-month parts and labour warranty on the work we do.
From the workshop
Real jobs off our ramps, described by the mechanic who did them.
A customer from Dudley brought in their Renault Captur diesel with a DPF fault. The filter itself turned out not to be the problem. The pipe that runs from the DPF to its pressure sensor was blocked, so the sensor was not getting a reading.
That pressure reading is how the car works out how full the filter is. With nothing coming through the pipe, it cannot tell, and that is how a perfectly good filter ends up being replaced.
Elliot cleaned the pipe out with DPF cleaner and a drill with a bike gear cable inserted. It saved the customer having a new DPF fitted.
A Stourbridge customer brought this one in with a simple complaint: no power. The diagnostics gave a less simple answer. The diesel particulate filter was reading 400 per cent full, which is the figure on the scanner in the photo, and that is not a number everyday driving produces.
A DPF traps soot from the exhaust and burns it off periodically. This one had blocked solid because a component had failed rather than because of how the car was being driven: the exhaust temperature sensor that should have been managing that burn-off was dead. With the filter off the car, it was completely blocked.
Rather than a new filter, the customer chose a secondhand unit that we had professionally cleaned, which saved a good deal of money. That went on along with a new lambda sensor and a new exhaust temperature sensor, then every fault code was cleared and the system values reset to zero. To be clear about what that means: the filter was replaced, not deleted. Removing a DPF is illegal and an automatic MOT failure, and we do not do it.
Then a road test. Elliot's word for the difference against how it arrived was unbelievable. Running perfectly.
DPF work is ramp work. Reading the filter properly, taking it off where it needs it and fixing the sensors or valves around it all happens at our workshop at Unit 6, Turner Street, Dudley, DY1 1TX.
Drop the car in, or we collect it from home or work and bring it back when it is finished. If it is in limp mode and you would rather not drive it, tell us and we will sort out getting it to us.
Call and describe what it is doing. We will tell you what we think it is before you commit to anything.
You will see DPF removal advertised. If your car was built with a filter, it is illegal to drive it with the filter taken out, and a missing filter is an MOT failure. The government says the fine can be up to £1,000 for a car and £2,500 for a van.
A blocked filter gets regenerated, cleaned or replaced, and the fault that blocked it gets fixed. That is the only kind of DPF work we do.
MOT testing with collectionBefore winter
The cheapest DPF repair is the one you never need. If your diesel mostly does short runs, a proper drive at a steady speed every week or two keeps the filter regenerating. A thermostat stuck open stops the engine getting hot enough, so a lukewarm heater is worth mentioning when you book.
Our winter check covers the battery, antifreeze, tyres, lights and heater. And if you are buying a used diesel, a pre-purchase inspection with a diagnostic scan shows stored DPF faults the seller may not mention.
In their words
What can I say?? Absolutely fantastic service from start to finish. That dreaded feeling you have when you need to find a new mechanic and worry about if you're getting a cowboy or going to be ripped off, well that's one thing I'm confident is not gonna happen with Elliot. So my car engine warning light come on, keeps going in limp mode practically unusable I've tried about 3 other garages prior to this one none would give me idea of prices, availability etc I found your local mechanic online and dropped them a message via WhatsApp got a response within 30 mins booked to come out to my house the next day for diagnostics. Elliot kept me updated did diagnostics, showed me faults, explained what needs to be done and how much he could do it for. No pressure to use him it was my informed decision his quote was a lot less than I expected and that included repairs, parts and a full service as that was due agreed. Elliot was flexible to my needs and availability fitted around me, kept me updated throughout and when I drove away my car felt like a new car again everything felt tight like when you get a new car, engine sounds quieter all round satisfied customer. I have found my new go to mechanic. Straight forward honest advice, flexible to my needs, good fair prices and all round genuine bloke if you want a trusted person who isn't trying to mug you off and scam you out of as much as they can then use these guys highly recommend
Rico Buenas
Verified customer
Excellent service from start to finish. Great communication throughout, very helpful and professional approach. The repair was carried out quickly, and they really helped me get my car back on the road as soon as possible. I really appreciate the support, honesty and efficiency. Highly recommended and I would definitely use their services again!
Karol Konik
Verified customer
Had cambelt and water pump change on volvo xc60 2.4 d4 at a great price, Fast turn around, an exellent mechanic Elliot is! Will reccomend to anyone.
Stuart Ratcliffe
Verified customer
We'll always tell you honestly what the filter needs, and what it doesn't.
We collect from across the area and bring the car back when it is done.
Workshop: Unit 6, Turner Street, Dudley, DY1 1TX. Open Mon-Sun, 7am-5pm.
55+ years between them. 12 months or 10,000 miles parts and labour warranty. £5m public liability cover.
Every job is carried out by Elliot or Keith - the mechanic who quotes your job is the one who works on your car. No call centres, no subcontractors.
Lead Mechanic & Founder
Founder of Your Local Mechanic. City & Guilds Level 3 qualified with 15+ years experience, specialising in modern diagnostics and hybrid vehicles across the Black Country.
Senior Mechanic & MOT Assessor
Senior mechanic at Your Local Mechanic with 40+ years Vauxhall main dealer experience and a fully qualified MOT assessor, known for honest, careful work across the Black Country.
Before you call
It means the diesel particulate filter is filling with soot faster than the car can burn it off. The filter cleans itself by getting very hot, a process called regeneration, and short, cold trips stop that happening. On most cars the right kind of drive clears the light. If it does not, or it keeps coming back, the filter or something feeding it needs looking at.
Why diesels block up in winter, and how to clear the lightOften, yes. Around twenty minutes at a steady speed on a dual carriageway or motorway, holding about 2,000rpm or more, usually lets the filter regenerate. Check your handbook, because the advice varies between makes. If two good runs have not cleared it, stop trying. Carrying on with short trips only loads the filter further.
For a short while, if the car is driving normally and no other warning lights are on. Ignore it for weeks and the filter keeps loading until the car drops into limp mode. By then a run will not fix it and the job costs more, so it is worth acting on early.
A regeneration started with diagnostic equipment rather than by driving. The car is held at a fast idle while the system raises the exhaust temperature to burn the soot off. It works on a heavily loaded filter that is not packed solid. Past a certain point the system will not allow it, and the filter needs cleaning or replacing instead.
It depends on how full the filter is, what it is full of, and whether it is physically damaged. A filter loaded with soot can often be regenerated or cleaned. One full of ash, cracked or melted needs cleaning off the car or replacing. We read it first and tell you which yours is, with the reason, before anything is done.
If it blocks again even with good runs, something is stopping it regenerating or making the engine produce extra soot. A failed exhaust temperature or pressure sensor, a sticking EGR valve, a worn injector, a thermostat stuck open or the wrong engine oil are the usual causes. That is what diagnosis is for.
How a full diagnostic scan worksDiagnostics is £45 and always comes first, because a DPF light can come on for a number of reasons. A forced regeneration is £250, including an oil and filter change. A clean off the car starts from £299, depending on the car. An on-car clean or a replacement filter is quoted after diagnosis, and you get a fixed price before any work starts.
No. If your car was built with a diesel particulate filter, it is illegal to drive it with the filter taken out, and a missing filter is an MOT failure. The government says the fine can be up to £1,000 for a car and £2,500 for a van. A blocked filter gets regenerated, cleaned or replaced, and the fault that blocked it gets fixed.
They can help a filter that is only partly loaded, alongside a proper run, because they help the soot burn at a lower temperature. They will not unblock a filter that has already put the car into limp mode, and they will not fix a faulty sensor or a sticking EGR valve.
It can. A DPF or engine management warning light that stays on is a problem at the MOT, and since 2018 any visible smoke from the exhaust of a diesel with a DPF is a major fault. If your DPF light has been on, sort it before the test rather than after.
Book an MOT with collectionDPF work is ramp work, so it is done at our workshop at Unit 6, Turner Street, Dudley, DY1 1TX. If the car is still driving we can collect it and bring it back. If it is in limp mode and you would rather not drive it, tell us and we will sort out getting it to us.
How collection and call-outs workTell Elliot or Keith what the car is doing and which model it is. You'll get a straight answer on whether a run might clear it, what it will cost to find out for certain, and whether it is safe to keep driving.
We reply to calls and messages typically within the hour.