- An emission system problem indicates a malfunction with the vehicle’s emission control parts, like the catalytic converter, oxygen sensors, or the EVAP system
- The issue is often signaled with an illuminated check emission system light, or for most modern cars, with the check engine light.
- Common causes include a loose gas cap, bad oxygen sensors, or vacuum leaks (Honda-specific issues like 2016-2017 Pilot fuel injector problems).
- Driving while the check emission system light is on can be risky, potentially causing engine damage, failed smog tests, or fines in strict states.
An emissions system problem warning appears on your dashboard & indicates that there is a problem with the system that keeps your car’s exhaust clean. You’ll typically see a check engine light illuminated. Most vehicles that are manufactured after 1996 no longer have the “check emissions system” light.
Whether you are driving a 2016 Honda Pilot, Odyssey, or some other Honda model, ignoring any warning could lead to engine damage, failing an emissions test, or even harming the environment.
What is an Emissions System?
The emissions control system in your car is like its environmental gatekeeper, catching harmful pollutants from the exhaust. Its major components include:
- Catalytic Converter: Converts toxins & harmful substances, such as carbon monoxide, into less harmful substances.
- Oxygen (O2) sensors: Measure the oxygen in the exhaust in order to ensure the combustion is cleaner by adjusting the air-fuel mixture.
- Evaporative emissions control (EVAP) system: Prevents fuel vapors from leaking into the atmosphere.
- Exhaust Gas Recirculation (EGR) valve: Converts gases coming back into the combustion chamber to reduce nitrogen oxides.
Mass Airflow (MAF) or Manifold Absolute Pressure (MAP) sensors: Ensure correct airflow to obtain the right air-fuel ratio.
Common Causes of Emissions System Problems
That pesky warning light could illuminate for numerous reasons, from inexpensive fixes to major repairs. Here are the usual culprits for why your vehicle could have an emissions system problem:
Loose or Broken Gas Cap: A loose gas cap permits the escape of fuel vapors to trigger the EVAP system. This is the simplest fix, costing around $10-$30.
Defective Oxygen Sensor: Defective O2 sensors (code P0420) modify the fuel mixture, causing your car to perform poorly & emit increased emissions.
Bad Catalytic Converter: A clogged or damaged catalytic converter will not adequately clean the exhaust gases, and is commonly tied to the P0420 codes.
Issues with the EVAP system: A faulty purge valve or a leaky charcoal canister (code P1457) allows gas vapors to escape & occurs frequently in Hondas.
Bad fuel or fuel system issues: Low-quality fuel and/or clogged injectors were associated with misfires & possibly increased emissions.
Vacuum leaks or exhaust leaks: Cracked hoses or an exhaust leak allow for rich fuel mixtures, which contribute to increased emissions.
Bad EGR Valve or faulty MAF/MAP sensors: A stuck EGR valve or a dirty MAP sensor (code P0101) would reduce combustion efficiency.
Wiring or Connection Issues: Corroded or loose wiring to your car’s sensors can send false signals to trigger the light.
Automobile technician Anthony Harlin says, “Any fault triggering the check engine light can be considered emission-related since they impact the vehicle’s performance & emission output.”
Honda-Specific Emission Issues
Honda owners, especially with model years 2016-2017 Honda Pilot or Odyssey, could be experiencing model-specific emissions issues. Web forums and reading the recall lists bring some of these issues to light:
2016-2017 Honda Pilot: Recalls are issued for faulty fuel injectors, as they caused misfires and emissions codes P0420 (catalytic converter issues) or P0171 (lean mixture). They also updated the software for the ECM (engine control module), which controlled sensor faults & inaccuracies.
Honda Odyssey: The EVAP system, mostly from the charcoal canister or the purge valve, would often trigger code P1457 from vapor leaks.
Other Hondas: Other Honda models, including CR-V, Accord, and others, have seen O2 sensor and catalytic converter failures after 100,000 miles due to poor-quality gas.
Also Read: Is 200,000 Miles Bad For A Used Car?
How to Diagnose an Emissions System Problem
Identifying an emissions system problem is like being a car detective, but you can start by checking the gas cap, inspecting the emission-related components, and calling for a mechanic.
- Check the Gas Cap: This is often the simplest solution. Make sure it is tightly fastened and avoid one that is cracked. Loose caps are known to cause EVAP codes (example: P0457).
- Note Symptoms: Check for rough idle, sluggish acceleration, excessive fuel use, or a rotten egg odor. These usually point to misfires or a failing catalytic converter.
- Use an OBD-II scan tool: Scan tools are simply attached directly to the OBD-II port located under the dashboard (for post-1996 vehicles).
- Inspect Components: Next, you can check the O2 sensors, the EVAP canister, the purge valve, & the vacuum hoses for any damage. Listen for hissing sounds (vacuum leaks) or visually inspect the exhaust pipe for rust, as noted in the second reference.
- Consider Consulting a Mechanic: If the codes are unclear or if the components you investigated or the other DIY strategies did not work, then visiting a mechanic could be worth a shot.
Your nearest Autozone offers a free scan if you don’t have an OBD-II scanner.
How Do You Fix Emissions System Problems?
Once you’ve identified the problem, you can either fix an emissions system issue yourself or you can have a mechanic do it.
DIY Fix
- Tighten or Replace Fuel Cap: If the cap is loose or damaged upon inspection, you can tighten or replace it. It might cost you $10-$30. Drive a few drive cycles to see if the issue clears.
- Use Catalytic Converter Cleaner: If you have a small blockage on the converter (P0420), you could try Cataclean, which costs around $20-$40 and can flush the catalytic converter.
- Clean MAP Sensor: If it is your MAP (P0101) sensor, you can spray it with MAF (mass air flow) cleaner, which costs $10-$15, and put it back in.
- Address Bad Gas: If it is indeed bad gas, you could buy better quality gas & use a fuel system cleaner (cost $10 – $20) to clear injectors.
Professional Repairs
| Repair Type | Estimated Cost |
| Replace Oxygen Sensor | $100-$300 |
| Replace Catalytic Converter | $1,000-$3,000 |
| Fix EVAP System (Purge Valve/Canister) | $150-$500 |
| Replace EGR Valve | $200-$400 |
| Repair Wiring or Exhaust Leaks | $100-$600 |
After repairs, the light can be turned off with an OBD-II code scanner, or you can disconnect the battery for 10 minutes. If the issue persists, the light stays on.
What happens if I don’t fix emission issues?
Not fixing emissions could lead to catastrophic damage to the engine, costing well over $1,000 to repair. You might also bear an inability to pass a smog test, penalty fees, and increased pollution.
Frequently Asked Questions (FAQs)
Why does my Honda say emissions system problem?
When your Honda lights up with a warning message that says, “emissions system problem,” there is a malfunction with the emissions system. Issues can include a loose gas cap, a defective oxygen sensor, or an EVAP problem.
Can bad gas cause emissions problems?
Yes. Low-quality fuel can clog injectors or foul sensors & trigger trouble codes like P0171 (lean mixture) or P0420 (catalytic converter).
Is it safe to drive my car with an emissions system problem?
Yes, but it would be risky. I don’t recommend it. It can be completely safe to drive with a loose gas cap, but it can also be extremely unsafe to drive with a bad catalytic converter (which can cause damage to the engine, depending on how bad it is). Or, you could be fined for failing the emissions test.
How do you reset the check emission system?
You can either clear the trouble code with the OBD scanner or, once you have addressed the issue, you can simply disconnect the battery for ten minutes. But if the issue occurs again, the message will still come back on.
How much does it cost to fix an emissions system problem?
Fixing an emissions system problem can take anywhere from $10 for a simple gas cap fix to $3,000 for repairing the catalytic converter.
What is the Honda emissions warranty?
Honda’s emissions warranty covers the parts that have a deemed material or workmanship defect on the emissions control systems for three years, or 60,000 km, whichever comes first.
For certain components like the catalytic converter & the Engine Control Module (ECM or PCM), the warranty has been extended to 8 years or 130,000 km, whichever comes first.
Check your VIN to see if you’re eligible.
Final Thoughts
There’s no point risking your car’s health even if it’s a minor fix. I’d highly suggest that you don’t let bad gas or missed maintenance turn a simple fix into an expensive repair. Either grab an OBD-II scanner or see your nearest mechanic if you notice any issues with the emissions system.
