Evaporative Emission System Vent Valve Control Circuit Low
The P0498 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission System Vent Valve Control Circuit Low. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $50 - $250 (parts and labor)
A cracked or loose gas cap causes 60%+ of EVAP codes. This $8 replacement clears P0442, P0455, and P0457 more often than any other repair.
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If a new gas cap does not clear it, the leak is somewhere in the EVAP plumbing. A smoke machine finds the exact leak -- a cracked hose, bad seal, or stuck vent valve -- in minutes instead of guessing at parts.
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Clear the code after the repair. If the light stays off after 50 miles, you just saved $200+ in shop fees.
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Common Symptoms
- Check Engine Light on
- Failed EVAP leak test
- Fuel tank pressure abnormalities
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Short to ground in vent valve control wiring Very High
- Failed EVAP vent valve solenoid (internal short) High
- Corroded connector at vent valve Moderate
- ECM vent valve driver circuit failure Low
Step-by-Step Diagnostic Procedure
-
Disconnect the EVAP vent valve connector and check for a short to ground on the control wire
-
Measure vent valve solenoid resistance; very low reading indicates an internal short
-
Inspect the vent valve connector for corrosion; the valve is typically located near the charcoal canister and exposed to road debris
-
Verify ECM output voltage on the vent valve control circuit with the valve disconnected
Common Fixes by Vehicle
What techs usually find when diagnosing P0498 on specific vehicles — tap your vehicle for the fix and the exact part:
2006-2015 Honda Civic/Accord/CR-V 2.0L/2.4L moderate DIY
P0498 on Honda means the canister vent shut valve circuit has low voltage. The valve is on top of the charcoal canister above the rear axle. The internal solenoid winding shorts or the connector fills with moisture. Replace the vent shut valve (Honda 17310-SDA-A02 or equivalent). Clean and dielectric-grease the connector before reassembly.
Labor: 1 hour2005-2012 Acura TL/MDX 3.5L/3.7L moderate DIY
P0498 on Acura V6s is usually the CVS (canister vent solenoid) valve failure. The OE part is pricey; Dorman 911-610 is a solid aftermarket replacement. Access is from under the vehicle at the fuel tank. Also check the valve's mounting bracket for rust -- if the bracket fails the valve grounds against the chassis intermittently.
Labor: 1 hour2007-2013 Honda Odyssey/Pilot 3.5L moderate DIY
Odyssey and Pilot P0498 points to the canister vent shut valve under the body near the fuel tank. Rust on the mounting bracket and moisture in the connector are the two failure modes. Replace the valve, clean the connector with contact cleaner, and apply dielectric grease. If rust has seized the valve, a propane torch applied to the metal housing (not the plastic) helps break it free.
Labor: 1-2 hoursFrequently Asked Questions
What is the EVAP vent valve?
The EVAP vent valve controls airflow into the charcoal canister. During purge cycles, it allows fresh air into the canister to push fuel vapors to the engine. During leak testing, it closes to seal the system for pressure testing.
Where is the EVAP vent valve located?
The vent valve is typically located on or near the charcoal canister, which is usually under the vehicle near the fuel tank or in the rear of the vehicle. Its location makes it susceptible to road debris and moisture damage.
Will P0498 affect my gas mileage?
P0498 typically will not noticeably affect fuel economy. The EVAP vent valve plays a role in emissions control rather than fuel delivery, so its malfunction primarily affects emissions test results and leak detection capability.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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