Engine management light on? Here's what it could mean
The engine management light, sometimes called the EML or the check engine light, is the dashboard warning that covers the widest range of possible faults. It can mean almost anything. But on a diesel car, there is one cause that comes up more often than almost any other: the DPF.
What the engine management light tells you
When the EML comes on, it means the ECU has detected a fault and stored a code in its memory. The light itself does not tell you what the fault is, only that a fault exists. The code it has stored does the actual explaining, and reading that code is the first step toward understanding what you are dealing with.
The EML is usually amber or orange and shaped like an engine silhouette, a block with a lightning bolt or with visible valve covers, depending on the manufacturer. It may flash (indicating an active, ongoing fault) or stay on steadily (indicating a stored fault that has been detected but is not currently triggering).
A flashing EML is more urgent and typically indicates a misfire or a fault that is actively damaging the engine. A steady EML means something has gone wrong and the car wants you to know, but is not necessarily in crisis right now.
Common EML causes on diesel cars
Diesels have more emissions-related components than petrol cars, which means more opportunities for EML triggers. The most common on modern diesel vehicles include:
The DPF sits near the top of this list in terms of frequency, particularly on vehicles used mainly for short urban journeys where the filter never gets the sustained heat it needs to self-clean.
Diesel particulate filter
soot accumulation, pressure sensor fault, or filter efficiency below threshold
EGR valve
exhaust gas recirculation valve sticking open or closed
Oxygen or NOx sensor
worn or failed sensor giving incorrect readings
Turbocharger
boost pressure outside expected range
Fuel injectors
misfiring or incorrect delivery quantity
Identifying a DPF fault
You do not need specialist equipment to read a fault code. A basic OBD-II reader, available for under £20 online, will connect to the port beneath your steering column and display any stored codes within seconds. Two codes point directly to the DPF:
Either of these codes alongside the EML is a clear signal that the DPF is the cause. You may also see pressure sensor codes (typically P2452, P2453, P2454) which relate to the sensor that monitors DPF blockage rather than the filter itself.
If you see any of these codes, do not clear them and wait. The fault will return, and in the meantime the blockage can worsen.
What to do next
Once you have confirmed the EML is DPF-related, the filter needs to be cleaned. Manchester DPF Cleaning provides a mobile chemical flush service across Greater Manchester. We carry out the clean at your location, home, workplace, or wherever the car is, using a professional chemical process that breaks down the soot deposit and restores the filter to normal operation.
Fixed price: £275. No garage, no tow truck, no waiting. Call 0161 694 7331 to book.