P0499 low

Evaporative Emission System Vent Valve Control Circuit High

The P0499 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission System Vent Valve Control Circuit High. This is a low severity code.

My Garage →

Keep driving?: Yes, but fix soon
DIY difficulty: moderate
Estimated cost: $50 - $250 (parts and labor)

Try This First ($8 Fix)

Stant 10838 OE Fuel Cap

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.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Find the Leak

THIKPO Automotive Smoke Machine

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.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Clear the Code

ANCEL AD310 OBD-II Scanner

Clear the code after the repair. If the light stays off after 50 miles, you just saved $200+ in shop fees.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Common Symptoms

Check Engine Light on
EVAP system unable to seal for leak test
Fuel vapor odor
Failed emissions test

Probable Causes (Ranked by Likelihood)

Short to power in vent valve control wiring Very High
Vent valve solenoid stuck energized (closed) High
Wiring harness damage near charcoal canister area Moderate
ECM vent valve control driver stuck high Low

Step-by-Step Diagnostic Procedure

Disconnect the vent valve connector and check for voltage on the control wire with key off; voltage present indicates a short to power
Test the vent valve solenoid for proper resistance and mechanical operation
Inspect wiring from ECM to vent valve for chafing or damage from road debris
Command the vent valve open and closed using a scan tool to verify ECM can control it

Common Fixes by Vehicle

What techs usually find when diagnosing P0499 on specific vehicles — tap your vehicle for the fix and the exact part:

2008-2016 Nissan Altima/Maxima 2.5L/3.5L moderate DIY

P0499 on Nissan = EVAP vent control circuit high voltage. The vent valve is at the rear of the vehicle on the EVAP canister. The valve solenoid opens internally causing a high-side circuit fault. Replace the vent valve with Nissan 14935-1AA0A or equivalent. Inspect the vapor lines for damage from debris -- these run along the frame rail.

Labor: 1 hour

Common fix part EVAP Vent Control Solenoid View on Amazon→ Compare fitment at PartsGeek→

2005-2014 Toyota Tacoma/4Runner 4.0L moderate DIY

P0499 on Toyota trucks is the EVAP canister vent valve assembly (Toyota calls it the 'CCV'). Spider webs, mud, and road debris block the air filter on top of the valve, causing a pressure/circuit fault. Clean or replace the valve and its filter. Also verify the fuel tank pressure sensor reads 0 inHg at rest.

Labor: 1 hour

Common fix part EVAP Vent Control Solenoid View on Amazon→ Compare fitment at PartsGeek→

2011-2018 Ford F-150 3.5L EcoBoost/5.0L moderate DIY

F-150 P0499 points to the EVAP vent solenoid (Ford calls it the Canister Vent Solenoid, CVS) on the canister behind the rear wheel. Motorcraft CX2224 is the correct replacement. A failed CVS will also trigger a gas-cap-like no-start EVAP warning on the cluster. Reset adaptive values after replacement with FORScan.

Labor: 45 min

Common fix part EVAP Vent Control Solenoid View on Amazon→ Compare fitment at PartsGeek→

Frequently Asked Questions

What does circuit high mean for P0499?

Circuit high means the ECM detects higher-than-expected voltage on the vent valve control circuit. This typically means the solenoid is receiving constant power, keeping it energized (closed) when it should be open.

Can a stuck vent valve cause fuel tank pressure issues?

Yes. If the vent valve is stuck closed, air cannot enter the charcoal canister. This can create a vacuum in the fuel tank during fuel consumption, potentially causing fuel pump strain and difficulty refueling.

Can I hear the vent valve operating?

Yes. When commanded by the ECM, you can usually hear a quiet click from the vent valve solenoid. If you command it with a scan tool and hear no click, the solenoid is likely stuck or the circuit is not reaching the valve.