Check Emission System Acura [Important Guide & Fix]

Seeing a “Check Emission System” warning light appear on your Acura’s dashboard can be concerning. This light typically indicates an issue with the vehicle’s emissions control system that needs to be addressed promptly to avoid potential engine damage.

In this comprehensive guide, we’ll cover everything you need to know about the check emission system warning on Acuras, including:

What Does “Check Emission System” Mean on an Acura?

The check emission system light on your Acura indicates that there is a problem with the vehicle’s emissions control system. This system is responsible for regulating and reducing the pollutants released from the exhaust system.

When this light comes on, it means one or more components related to the emissions system is malfunctioning. This could include:

Ignoring this warning light risks excess vehicle emissions and potential failure of an emissions test. It’s important to diagnose and repair the issue promptly to restore proper emissions function and avoid potential engine damage.

What is the EVAP System?

EVAP stands for Evaporative Emissions Control System. This system is designed to prevent fuel vapors in the fuel system from escaping into the atmosphere.

The EVAP system captures vapors from the fuel tank and temporarily stores them in a charcoal canister. When the engine is running, these vapors are purged from the canister and burned in the engine.

The main EVAP components include:

  • Purge valve
  • Charcoal canister
  • Fuel tank pressure sensor
  • Leak detection pump
  • Vapor lines

Problems with any of these components can cause check engine lights and EVAP related error codes. Common issues include cracked hoses, a faulty purge valve, or leaks in the system.

Common EVAP System DTCs

DTCDescriptionPossible Causes
P0440General EVAP system faultLeak in EVAP system, loose/faulty gas cap
P0441Incorrect purge flowStuck open purge valve, blockage in line
P0442Small leak detectedCrack or hole in EVAP hose, faulty gas cap
P0456Very small leak detectedDamage or hole in fuel tank, loose connection
P0455Large EVAP system leakDisconnected or damaged EVAP hose

Step-by-Step Diagnosis

If you see a check emission system warning, here are some steps to diagnose the cause:

1. Check for Loose Gas Cap

The first thing to check is whether your gas cap is loose or faulty. An improperly sealed fuel cap allows fuel vapors to escape, which can trigger the check emissions light. Remove the cap and ensure it seals tightly when re-installed.

2. Read Diagnostic Trouble Codes (DTCs)

Use an OBD2 scanner tool to read any diagnostic trouble codes (DTCs) stored in the computer. This will point you towards the specific component causing the issue. Common DTCs include P0440, P0441 or P0442 for EVAP system faults.

3. Inspect EVAP System

Based on the DTCs, inspect the related EVAP components. Look for cracked hoses, faulty valves, leak detection pump issues or a faulty charcoal canister. Repair or replace any faulty parts.

4. Check Oxygen Sensors

Faulty oxygen sensors can mimic an emissions control problem. Inspect sensor wiring and connectors. Replace any deteriorated or damaged oxygen sensors.

5. Inspect EGR System

Problems with the exhaust gas recirculation (EGR) system can also trigger the check emissions light. Check for carbon buildup in the EGR valve and related ports. Clean or replace faulty EGR components.

6. Repair Catalytic Converter

If your Acura’s catalytic converter is not functioning properly due to damage or contamination, it can cause emissions system codes. Replace a faulty catalytic converter to restore proper emissions function.

How to Reset Check Emission System Light

Once the underlying problem is fixed, you can reset the check emission system light by:

  • Disconnecting the battery for 10-15 minutes which erases stored DTCs
  • Using an OBD2 scanner tool to clear trouble codes
  • Driving for several drive cycles to trigger the self-diagnostic system

The check engine light will stay off once the emissions system is operating normally.

Oxygen Sensor Replacement Intervals

Sensor TypeRecommended Mileage Interval
Upstream O2 SensorEvery 60,000 miles
Downstream O2 SensorEvery 100,000 miles


Does a loose gas cap cause the check emissions light?

Yes, a loose or faulty gas cap is one of the most common reasons for the check emissions light. Always ensure the cap is properly sealed after refueling.

What triggers a P0440 code?

P0440 signifies an evaporative emissions system leak. This could be caused by a loose gas cap or leak in the EVAP system. Inspect the fuel cap, hoses, purge valve, and charcoal canister for cracks or damage.

Will the check engine light turn off on its own?

The light may turn off after several drive cycles if the underlying problem was minor and self-corrected. But more serious issues will keep the light on until repaired.

Is it safe to drive with the check emissions light on?

You can safely drive a short distance with this warning light on. However, the problem should be diagnosed and fixed promptly to avoid potential driveability issues or engine damage from prolonged driving.

Do I need to replace O2 sensors in pairs?

For optimum performance, it’s best to replace both upstream or downstream oxygen sensors rather than just one. Replacing them in pairs helps maintain proper fuel trim.

How do you repair a malfunctioning emission control system?

A faulty emission control system may be fixed by tightening or resetting the fuel cap, swapping out a leaking fuel cap for one with a better seal or vent, and fixing or replacing any potentially leaking parts like the carbon canister or vapor control valve.

The Bottom Line

If you see Check Emission System Acura on your dashboard, consider checking the gas cap first, as it might be a common culprit for triggering this warning. The check emission system light on your Acura indicates a problem with the emissions control system. Thorough diagnosis and prompt repair of the underlying issue is important to restore proper emissions function, pass inspections, avoid potential engine damage, and clear the warning light.

With proper maintenance and care of your Acura’s emissions components, you can help the vehicle run efficiently for many miles. Be sure to address any warning lights right away and perform recommended service at the scheduled intervals.

Ethan Simons
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