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P0499 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Evaporative Emission System Vent Valve Control Circuit High


What is the Evaporative Emission System Vent Valve Control Circuit High and what does it mean for your vehicle? 

The evaporative emissions system is designed to limit the fuel vapors from escaping into the air. Occasionally, the EVAP system will open the purge valve to bring in fresh air for the system.

However, if the EVAP system has not commanded a purge condition but detects that a high voltage pressure is present in this non-purge condition, it will alert the Powertrain Control Module (PCM) that there has been a malfunction in the evaporative emission system vent valve, or its control circuit.

Therefore, the PCM will store the P0499 code and will most likely trigger the Check Engine light to signify that there is an issue.


Common causes for this error code to appear are:

  • a faulty purge control solenoid or valve, 
  • a faulty EVAP canister vent valve,
  • a clogged charcoal canister or
  • a broken charcoal canister,
  • a cracked or broken vacuum or fuel vapor hoses or
  • a faulty pressure sensor. 

You also should check for blown fuses, which may indicate a more serious issue. When diagnosing the underlying cause of the P0499 code, a common misdiagnosis is to replace the EVAP emissions system components rather than checking for a vacuum leak or an improperly installed fuel cap.

These parts are more likely to be faulty than a part that needs replacement in many cases.

Symptoms and Repairs

Most of the time, the only sign there is a noticeable problem with the Evaporative Emission System vent valve is by your Check Engine light. However, your code reader will most likely read other emissions system code errors as well.

This is why you should have your vehicle brought in to be seen by a certified mechanic.

Once the OBD-II scanner detects the P0499 code, the automotive technician should then  inspect all of the wiring, connectors, and other electrical components of the emissions system.

Once the damage is accessed, the damaged parts should be replaced, reconnected, or repaired.

Then, the system can be retested once the code has been cleared from the PCM.

After this retest, the mechanic will be able to determine whether or not there is a problem with the EVAP emissions system, as the code will reappear.

He or she can then make any further repairs to the vehicle. To make sure that the error code is repaired correctly make sure that the fuel cap is properly installed, replace the faulty purge control solenoid or valve, replace the faulty EVAP canister vent valve and clean out a clogged charcoal canister or replace if it is broken charcoal.

 You also need to make sure that the cracked or broken vacuum or fuel vapor hoses are repaired or replaced. A faulty pressure sensor may also need replacing.

Blown fuses should also be replaced. However, remember that a blown fuse could signify a larger issue that will need to be checked and addressed.

Seriousness of Error Code P0499

The P0499 error code is a minor problem and therefore it should not affect the vehicle’s operation.

However, if left unrepaired it could cause the vehicle to fail an emissions test. If necessary, this problem can be fixed at the time of your next tune up or inspection. Generally, the cost of these repairs are minor at around $80.

Of course, this will depend on damage to parts in disrepair as well as the manual labor involved.

Related Trouble Codes

P0400 to P00499 codes refers to the Auxiliary Emissions control.

P0400 to P040F and P041A to P041E cover the exhaust gas recirculation flow, circuits or temperature sensor malfunctions.

Secondary air injection issues are under codes P0410 to P0419. Like the P0499 code, it too is a noticeable problem by the fact that the Check Engine light will come on.

These codes are picked up by the PCM when the exhaust gas recirculation flow monitoring criteria has not been met. Between trouble codes P0420 and P0440 include issues with the catalytic converter.

Again, this too is signified as a problem by the Check Engine light coming on. However, the vehicle’s performance is usually not affected by this. It is caused by problems with an insufficient catalytic converter, defective front or rear sensors or misfiring engines.  

Trouble codes between P0440 and P0455 refer to evaporative system malfunctions. It too is noticed only as an issue with a Check Engine light. It can be caused by missing or damaged fuel caps, a broken evaporative system hose, defective fuel tank sending unit, defective evaporative vent valve or a damaged fuel tank.  


The P0499 trouble code doesn’t have to cause chaos. Once a certified mechanic has confirmed that you have a Evaporative Emission System Vent Valve Control Circuit High issue then the problem should be relatively simple to resolve if done properly.

P0499 Code – What Does It Mean & How To Fix It