06/08/2021
The MOT Test: A Crucial Annual Check
The Ministry of Transport (MOT) test is a mandatory annual inspection for most vehicles over three years old in the United Kingdom. Its primary purpose is to ensure vehicles meet road safety and environmental standards. Over the years, the MOT test has evolved to keep pace with technological advancements in vehicles and to address emerging environmental concerns. One of the most significant overhauls in recent memory occurred on 20 May 2018, introducing a raft of new rules and classifications that affect vehicle owners across the country.
What Changed on 20 May 2018?
The MOT test underwent a substantial revision on 20 May 2018, bringing in new defect types, more stringent regulations for diesel car emissions, and exemptions for certain classic vehicles. These changes were designed to improve road safety and reduce vehicle emissions, particularly from diesel vehicles, which have come under increased scrutiny in recent years.
New Defect Classifications
Prior to the 2018 changes, defects were generally categorised as 'minor' or 'major'. The updated system introduced three categories:
- Dangerous: Vehicles with dangerous defects will not be allowed to drive and will fail the MOT. These issues pose a direct and immediate risk to road safety.
- Major: These are defects that could potentially compromise vehicle safety or harm the environment. A vehicle with major defects will fail the MOT.
- Minor: Minor defects are issues that do not pose a significant risk but should be monitored and repaired. A vehicle with only minor defects will pass the MOT, but the issues will be recorded on the MOT certificate.
This new classification system provides a clearer understanding of the severity of any issues found during the test, allowing owners to prioritise necessary repairs.
Stricter Diesel Emissions Rules
The 2018 MOT test brought about much tighter regulations for diesel vehicle emissions. This was a direct response to concerns about air quality and the prevalence of diesel particulates. A key change was the introduction of a visible smoke test from the exhaust pipe during normal acceleration. If the tester sees smoke of any colour, the vehicle will fail.
Furthermore, checks were enhanced for vehicles fitted with a Diesel Particulate Filter (DPF). The test now specifically checks if the DPF has been tampered with or removed. If a vehicle is found to have had its DPF removed or deliberately tampered with, it will automatically fail the MOT. This is a crucial point for owners of diesel vehicles, as the DPF plays a vital role in filtering harmful particulate matter from exhaust gases.
The user discussion highlights the impact of these changes, with one individual noting that authorities tightened regulations on exhaust gas analysers to catch those who had removed their DPFs. This reflects the government's commitment to tackling diesel emissions and ensuring that vehicles comply with environmental standards.
Exemptions for Older Vehicles
A significant change introduced on 20 May 2018 was the exemption from the MOT test for vehicles that are 40 years old or older. Previously, this exemption only applied to vehicles manufactured before 1 January 1960. The new rule means that any vehicle first registered 40 years ago or more is now exempt from the MOT test, provided there have been no substantial modifications.
This change acknowledges the historical significance of classic cars and the fact that they are typically well-maintained and driven less frequently than modern vehicles. However, it's important to note that owners of these exempt vehicles are still legally responsible for ensuring their cars are roadworthy and safe to drive.
Understanding DPFs and Emissions Testing
The conversation around DPFs (Diesel Particulate Filters) is particularly relevant in the context of the 2018 MOT changes. The DPF is a crucial component of modern diesel engines, designed to capture soot and particulate matter. Its removal or tampering can lead to significant emissions problems and, as of 2018, an automatic MOT failure.
What is a DPF?
A Diesel Particulate Filter (DPF) is a filter that is fitted into the exhaust system of a diesel vehicle. Its purpose is to remove diesel particulate matter (soot) from the exhaust gases. The DPF works by trapping the soot particles, which are then periodically burned off through a process called 'regeneration'. This process typically occurs automatically when the engine reaches a certain temperature and driving conditions are met (e.g., sustained higher speeds).
DPF Issues and MOT Failure
As mentioned, the 2018 MOT test introduced stricter checks for DPFs. If a DPF is missing, has been illegally removed, or has been modified in a way that bypasses its filtering function, the vehicle will fail its MOT. This has led to increased costs for diesel car owners, as replacing a faulty or removed DPF can be expensive.
The user's experience illustrates this point. They mention purchasing a non-badge DPF for their Peugeot for £287 fitted in October 2018, while the official Peugeot price was significantly higher. This suggests a market for aftermarket DPFs as a more affordable alternative to genuine parts, although the quality and longevity of these parts can vary.
Diagnosing DPF Problems
Diagnosing DPF issues can be complex. The user describes receiving 'anti pollution' and 'risk of filter blocking' messages before a regeneration cycle. They also detail how a piece of their EGT (Exhaust Gas Temperature) sensor snapped off, potentially damaging the DOC (Diesel Oxidation Catalyst), which sits just above the DPF. This led to an increase in the differential pressure, indicating a potential blockage or issue with the DPF system.
The user also highlights the importance of correctly informing the car's ECU (Engine Control Unit) that a new DPF has been fitted. This is done through diagnostic software, such as Diagbox, using a function called 'PACK REPAIR'. This process resets various parameters, including the FAP fluid level and the ash/soot counter, which is essential for the DPF system to function correctly and for the car to recognise the new component.
Cost of DPF Replacement
The cost of replacing a DPF can be substantial. Genuine DPFs from manufacturers like Peugeot can cost upwards of £600, with the associated catalytic converter potentially costing even more. Aftermarket DPFs, like the one fitted to the user's car, can be significantly cheaper, sometimes available for less than £200, especially with discount codes from parts suppliers. However, the user raises concerns about the quality of the aftermarket DPF fitted to their vehicle, as it appeared to have failed prematurely.
Key Takeaways for Vehicle Owners
The 2018 MOT test changes have had a significant impact on vehicle owners, particularly those with diesel vehicles. Here are some key takeaways:
| Aspect of MOT | Pre-2018 | Post-20 May 2018 |
|---|---|---|
| Defect Classification | Minor / Major | Minor / Major / Dangerous |
| Diesel Emissions | Standard checks | Visible smoke test; checks for DPF tampering/removal (Failure) |
| Age Exemption | Vehicles pre-1960 | Vehicles 40 years or older |
Maintaining Your Diesel Vehicle
For owners of diesel vehicles, particularly those with DPFs, regular maintenance is crucial. Ensure your DPF is functioning correctly and that no tampering has occurred. If you experience warning lights or messages related to the DPF, seek professional diagnosis promptly. Consider the implications of using aftermarket DPFs and research their quality and warranty provisions.
Choosing a Garage
When it comes to DPF replacement or repair, choosing a reputable garage is paramount. The user's experience highlights the potential for issues with part quality and installation. Always ask about the warranty offered on parts and labour. Understanding the diagnostic procedures, such as the 'PACK REPAIR' function for DPF replacement, is also important.
Frequently Asked Questions
Q1: When did the MOT test rules change significantly?
The MOT test rules saw significant changes on 20 May 2018.
Q2: What is the new defect classification in the MOT test?
The new classifications are Minor, Major, and Dangerous defects.
Q3: Will my diesel car fail the MOT if the DPF is removed?
Yes, a vehicle will automatically fail the MOT if its DPF has been removed or tampered with.
Q4: Are all older cars exempt from the MOT test?
Vehicles that are 40 years old or older are exempt from the MOT test, provided they haven't undergone substantial modifications.
Q5: How can I tell if my DPF needs attention?
Warning lights on the dashboard, reduced engine power, and messages like 'risk of filter blocking' are common indicators of DPF issues.
Conclusion
The MOT test changes implemented on 20 May 2018 marked a significant step towards ensuring vehicle safety and environmental compliance in the UK. The stricter rules for diesel emissions and DPF checks underscore the ongoing commitment to improving air quality. Understanding these changes is vital for all vehicle owners to ensure their vehicles remain road legal and safe.
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