Can You Still Pass an MOT After Emissions Deletes?
Emissions deletes—like AdBlue delete, DPF delete or EGR delete—are popular for improving reliability and avoiding costly repairs. But once you’ve removed or bypassed part of the emissions system, can your vehicle still pass its MOT? In this guide, we’ll explain the MOT emissions tests, how deletes affect them, and what drivers can expect.
Understanding the MOT Emissions Test
The MOT includes two key emissions checks:
- Tailpipe Test: Measures visible smoke levels or opacity under load (diesels) or exhaust gas composition (petrol).
- On-Board Diagnostics (OBD) Check: Verifies that the ECU has no active faults related to emissions systems (required on 2006+ petrol and 2011+ diesel vehicles).
If your vehicle fails either, it won’t pass the MOT until the fault is rectified.
How Deletes Impact MOT Requirements
Removing or disabling emissions components can affect each test differently:
- AdBlue Delete: Clears SCR-related fault codes so the OBD check sees no active errors. Tailpipe readings remain unaffected.
- DPF Delete: Permanently disables the diesel particulate filter. Smoke opacity may increase, risking a tailpipe fail if visible soot exceeds the limit.
- EGR Delete: Stops Exhaust Gas Recirculation. This generally has minimal impact on tailpipe opacity but removes an emissions control check in the ECU.
Real-World Scenarios
- Case 1: AdBlue Delete on a Transit Custom
After a delete, the OBD check passed with no SCR faults—MOT tester only sees the ECU cleared. Tailpipe opacity remained within limits, so the van passed. - Case 2: DPF Delete on a Ford Ranger
Visible smoke increased on heavy throttle, leading to an immediate tailpipe failure. The owner then opted for a mobile diagnostic and returned the stock file for MOT. - Case 3: EGR Delete on a BMW 320d
No visible smoke change and OBD scan showed no EGR codes. The vehicle passed with no issues.
Tips to Improve Your Chances
- Use Professional Deletes: Mobile services like ours use custom ECU files that correctly disable fault codes without affecting other systems.
- Clean the Tailpipe: A quick drive or forced regen before the test can reduce soot build-up.
- Perform a Pre-MOT Scan: Book a full diagnostic scan to clear any lingering codes.
- Revert If Needed: If a delete causes a tailpipe fail, you can revert to your original ECU file before the test.
Legal & Ethical Considerations
While some deletes may help you pass the MOT, remember that removing emissions controls is only legal for off-road, export, or motorsport vehicles. For daily road use, always consider the environmental impact and local regulations.
Our Mobile MOT-Prep Service
At iFixAdBlue, we offer a mobile MOT-prep package tailored for emissions-deleted vehicles:
- OBD fault code clear and ECU scan
- Smoke opacity check & forced regeneration (diesel)
- Re-installation of original ECU file if required
- Pass/fail consultation and on-site fixes
Learn more on our Diagnostics page.
Ready for Your Next MOT?
Whether you’ve had an AdBlue delete, DPF delete, or EGR delete, you can still prepare effectively for your MOT. Book our mobile diagnostic and MOT-prep service to clear codes, optimise emissions readings, and increase your chances of a first-time pass.
