Why does my Honda Pilot say emission system problem?

Your Honda Pilot is telling you that there’s a fault in the emissions-control system. In practical terms, the onboard computer has detected an issue—from a simple tightening of the gas cap to a deeper problem with EVAP components or sensors—that could affect exhaust emissions and fuel efficiency.

What the warning means

Honda uses the Emission System Problem message to indicate that the vehicle’s diagnostic system (OBD-II) has found a fault in the emissions control network. When the PCM (powertrain control module) identifies a fault through tests and sensor readings, it stores a diagnostic trouble code (DTC) and may illuminate the check engine light or display a service message like Emission System Problem.

How it relates to your Pilot’s emissions components

The emissions system covers fuel vapor recovery (EVAP), oxygen sensors, the catalytic converter, wiring, and related vacuum lines. A fault in any of these can trigger the warning without immediate drive-ability issues, though a serious fault may reduce power or fuel economy.

Common causes in Honda Pilot

The most frequent culprits behind this warning fall into a few broad categories. The following list highlights the typical issues that trigger the emission-system fault message on many Pilot models.

• Loose, cracked, or faulty gas cap, which can allow fuel vapors to escape and trigger EVAP tests


• EVAP system leaks or failures (cracked hoses, damaged canister, faulty purge or vent valve)


• Oxygen sensors (upstream or downstream) reporting abnormal readings


• Mass air flow (MAF) sensor or intake/Vacuum leaks affecting air-fuel mixture


• Fuel-pressure or fuel-delivery issues (fuel pump or regulator) affecting combustion and emissions


• Catalytic converter problems or degraded efficiency (often flagged by codes like P0420/P0430)


• Electrical wiring or connector faults to emissions sensors and the ECU

After the underlying issue is repaired, the PCM usually clears the fault and the warning may turn off after a few drive cycles, provided the problem no longer exists.

How to diagnose

Diagnosing an emission-system problem involves reading the stored codes, checking for obvious causes, and performing targeted tests. The following approach is common for a Honda Pilot:

• Obtain the trouble codes with an OBD-II scanner and note any related freeze-frame data


• Check the gas cap: tighten to the specified click, or replace if the cap is damaged


• Inspect the EVAP system for leaks ( visually inspect hoses and connections; a smoke test can help locate leaks)


• Look for vacuum leaks around the intake manifold, PCV valve, and associated hoses


• Evaluate oxygen sensors and the MAF sensor if codes point to sensor performance


• If codes indicate fuel-system or catalyst issues (e.g., P045x, P013x/P014x, P0420/P0430), perform targeted tests such as fuel pressure checks or catalytic converter assessment


• Consider professional diagnostics if the issue isn’t obvious or if the fault codes point to complex components

Diagnostics can vary in complexity and cost, but a systematic check from the simplest fix (gas cap) to more involved emissions components is standard practice.

What to do next

Act promptly to avoid longer-term emissions damage or reduced fuel economy. The following steps are commonly recommended when you see Emission System Problem on a Honda Pilot:

• Verify the gas cap is tight and in good condition; drive for a few cycles to see if the warning resets


• Read the OBD-II codes and document them for a repair shop or dealership


• Inspect for obvious EVAP leaks and sensor issues; pursue a smoke test if leaks aren’t visually evident


• Address any due maintenance or wear in EVAP components, oxygen sensors, or the MAF sensor as indicated by codes


• If the light is flashing, or there are symptoms like rough idle, misfires, or loss of power, reduce driving and seek service promptly to prevent potential damage to the catalytic converter


• Consult a qualified technician for a definitive diagnosis and repair plan

Costs can vary widely depending on the exact cause. A simple gas-cap fix is inexpensive, while EVAP repairs, sensor replacement, or catalytic-converter work can be significantly more costly.

Estimated costs to expect

Understanding likely ranges can help you plan. The following figures are typical ballpark estimates and can vary by model year, location, and labor rates.

Before the list: note that diagnostic charges may apply, and actual repair costs depend on the underlying problem.

• Diagnostic test: typically $50–$120


• Gas cap replacement: approximately $10–$60 for parts (labor may add)


• EVAP purge valve: about $150–$400 for parts plus labor


• EVAP canister or related components: roughly $200–$800 for parts plus labor


• Oxygen sensor(s): around $80–$300 per sensor (parts plus labor)


• Mass air flow sensor: about $60–$250 for parts plus labor


• Vacuum hoses and lines: typically $40–$150 for parts plus labor


• Catalytic converter replacement: commonly $800–$2,500 or more for parts plus labor

Prices vary by dealership vs. independent shop, and some emissions issues may be covered under warranties or recalls if applicable.

When to seek help

Seek professional help if you’re unsure about the codes or the cause, or if symptoms accompany the warning. Immediate attention is warranted if the vehicle exhibits misfiring, reduced power, stalling, or a strong fuel odor, as these can indicate problems that could damage the catalytic converter or exhaust system.

• If the check-engine/Emissions light is solid, schedule a diagnostic visit soon


• If the light is flashing or you notice rough operation, pull over safely and seek roadside assistance if needed

Regular maintenance and prompt attention to emissions-related warnings help preserve fuel economy and prevent more expensive repairs down the line.

Summary

The Emission System Problem message on a Honda Pilot signals a fault in the emissions-control network. Common causes range from a loose gas cap to EVAP leaks, faulty sensors, and catalytic-converter-related issues. Start with simple checks (gas cap, codes), perform targeted diagnostics (EVAP tests, sensor tests, pressure checks), and pursue professional repair as indicated by the diagnostic results. Addressing the issue promptly can protect your vehicle’s performance, emissions, and long-term costs.

How to fix an emissions system problem?

To fix an emissions system problem, first, check for simple fixes like a loose gas cap or a clogged air filter. If the problem continues, use an OBD-II scanner to diagnose trouble codes and identify issues such as a faulty oxygen sensor or catalytic converter. Next, replace any damaged components, repair leaks, and then use the scanner or disconnect the battery to clear the warning light, remembering that clearing the light does not fix the underlying problem. 
1. Perform basic checks and fixes 

• Check the gas cap: Ensure it's on tightly, and replace it if the seal is broken or loose, as this is a common cause of the warning light. 
• Inspect the air filter: A dirty air filter can cause emissions issues, so clean or replace it. 
• Check for other warning lights: If other lights like low oil pressure or overheating are on, pull over safely and contact a professional, as these are more urgent issues. 

2. Use a diagnostic tool 

• Read the trouble codes: Use an OBD-II scanner to read the stored trouble codes. These will provide specific information about the problem, such as a faulty oxygen sensor or a clogged catalytic converter. 
• A blinking light is an emergency: A solid light means you should get it inspected soon, but a blinking light indicates a more serious issue that requires immediate attention from a professional. 

3. Repair or replace faulty components 

• Replace faulty sensors: This includes the oxygen sensor, which regulates the fuel-air mixture. 
• Address leaks: A technician can perform a smoke test to find and repair leaks in the exhaust or EVAP systems. 
• Inspect the catalytic converter: This is a more expensive repair, but the "rotten egg" smell is a key indicator of a problem here. 
• Check electrical connections: Look for any damaged wiring or leaking vacuum hoses that may be causing the problem. 

This video demonstrates how to fix emission codes cheaply: 59sBUILT OFFICIALYouTube · Feb 25, 2018
4. Clear the warning light 

• Use the scanner: After repairs are made, use the OBD-II scanner to clear the codes and turn off the light. 
• Disconnect the battery: If you don't have a scanner, you can disconnect the negative battery terminal for about 30 seconds to reset the computer. However, this may also reset "ready codes" needed for emissions testing. 

5. Prevent future issues

• Follow a regular maintenance schedule: This includes regular oil changes and tune-ups. 
• Use high-quality fuel: This helps prevent damage and buildup in the emission control system. 

What is the emission system problem on the Honda Pilot?

An "emissions system problem" on a Honda Pilot is often caused by a faulty oxygen sensor, a clogged catalytic converter, or issues with the fuel injectors, which can be more common in 3rd generation models. Other causes can include exhaust leaks, problems with the evaporative emissions (EVAP) system, or issues with the cylinder deactivation system. The first step to diagnosing the problem is to use an OBD-II scanner to read the specific trouble codes, as the warning light alone doesn't point to a single issue.
 
Common causes and symptoms

• Oxygen sensors: These sensors monitor oxygen levels and can fail over time due to age, contamination, or wiring issues. Symptoms include poor fuel efficiency and a lit warning light. 
• Catalytic converter: A failing catalytic converter can be caused by age or contamination from other issues, such as oil leaks. Symptoms include a loss of power and sluggish acceleration. 
• Fuel injectors: Direct injection models, especially the 3rd generation (2016-2022), can have faulty fuel injectors that trigger the emissions light. This may require replacement and could be covered under an extended warranty. 
• Exhaust system: Leaks in the exhaust pipes or other components can set off the warning light. 
• EVAP system: Problems with the evaporative emissions system, such as a faulty purge valve, can cause the warning light to appear. 
• Cylinder deactivation system: In models with cylinder deactivation, a fault in this system can trigger a related emission control fault. 

This video explains the meaning of the "Emissions System Problem" light on a Honda Pilot: 1mSimple Mechanic AdviceYouTube · Oct 31, 2024
How to diagnose and fix the problem

1. Use an OBD-II scanner: The first step is to scan the vehicle's computer for specific trouble codes, as this will help pinpoint the exact cause. 
2. Check for loose gas cap: Although Pilots don't have a traditional gas cap, the EVAP system can still trigger a warning if there's an issue, like a bad purge valve. 
3. Inspect for exhaust leaks: Look for any visible holes or damage in the exhaust system. 
4. Check for other issues: Look for other symptoms like rough idling, decreased fuel efficiency, or unusual exhaust smoke. 
5. Consider a professional diagnosis: Some issues, like a bad catalytic converter or fuel injectors, may require professional diagnosis and repair. It may also be beneficial to check if your vehicle is eligible for an extended warranty for the affected components. 

You can watch this video to learn how to fix the "Emissions System Problem" light on a Honda Pilot: 1mRondon Fuxe BoxYouTube · Oct 15, 2025

Can you drive a Honda with the emission system problem?

Can I still drive my car with the “Check Emission System” warning light on? It's not recommended to drive with the Check Emission System warning light on until you know the cause. Long-lasting damage and extensive repairs can result.

How much does Honda charge for emission system check?

between $61 and $90
The average cost for a Honda Civic Emission Control System Inspect is between $61 and $90. Labor costs are estimated between $61 and $90. This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.