A failed emissions test can be frustrating—especially if it interrupts your vehicle registration, compliance schedule, or fleet operations. But don’t panic. If you’ve recently received a fail report after an emissions test in Ontario, there are clear steps you can take to resolve the issue and get back on the road.
In this guide, we’ll walk you through:
- Why emissions tests fail
- What repairs may be required
- How much it might cost
- What to expect during a retest
Why Did Your Vehicle Fail the Emissions Test?
There are two main reasons a commercial diesel vehicle may fail an emissions test in Ontario:
1. Failed Opacity Test
The opacity test measures how much smoke your vehicle emits under load. Emission limits vary by model year.
| Model Year | Maximum Opacity Allowed |
| 1990 and older | 40% |
| 1991–2007 | 30% |
| 2008–2010 | 20% |
| 2011 and newer | 10% |
If your truck or bus emits smoke beyond these thresholds, you’ll fail the test.
2. Failed On-Board Diagnostic (OBD) Test
If your vehicle is from 2007 or newer and has a GVWR of up to 6,350 kg, it must also pass an OBD scan. Common failure reasons include:
- Malfunction indicator light (check engine light) is on
- Diagnostic Trouble Codes (DTCs) related to emissions systems
- Incomplete monitor readiness
- Damaged or tampered OBD port
What to Do After Failing the Emissions Test
If your emissions test failed, here’s what to do next:
Step 1: Review the Test Report
Your DriveON-certified technician will provide a fail report that outlines:
- The exact reason for the failure
- The emissions test component that failed (opacity or OBD)
- Any visual inspection issues, if applicable
Step 2: Schedule Repairs
You are not required to repair the vehicle at the same inspection location. Choose a licensed diesel mechanic who understands emissions systems. Common repair needs include:
- Replacing clogged diesel particulate filters (DPFs)
- Repairing EGR or SCR systems
- Fixing exhaust leaks
- Replacing sensors (NOx, oxygen, or pressure sensors)
Step 3: Book a Retest
Once repairs are complete, return to the same DriveON Vehicle Inspection Centre (VIC) or mobile testing provider within 10 days to take advantage of reduced retest fees.
Emissions Test Cost Breakdown (Ontario)
| Service | Estimated Cost Range |
| Initial emissions test | $90–$150 |
| Retest (within 10 days) | $30–$75 |
| Common repairs (DPF cleaning, sensors, etc.) | $300–$1,500+ |
Prices vary depending on vehicle type, condition, and repair complexity. Fleet discounts may be available through mobile testing partners.
How to Avoid a Failed Emissions Test in the Future
Preventive maintenance is key to passing on the first attempt. Here are a few best practices:
- Maintain your diesel particulate filter and SCR system
- Monitor fuel quality and perform regular oil changes
- Fix the check engine lights immediately
- Run regular diagnostic scans with a code reader
- Avoid tampering with OBD connectors or emissions hardware
If your fleet operates year-round, consider scheduling tests a few weeks before your registration deadline to allow time for repairs if needed.
Final Thoughts
A failed emissions test in Ontario isn’t the end of the road—but it is a signal that your vehicle needs attention. With the right repairs and a fast retest, you can stay compliant and avoid disruptions to your operations.
Looking for a certified, mobile emissions retest near you?
We provide DriveON-approved testing at your location, helping commercial vehicle owners and fleet managers minimize downtime and stay compliant.
