Emissions

P0498 — EVAP Vent Valve Control Circuit Low

Severity: low Safe to drive

What P0498 means

The EVAP vent valve lets the charcoal canister breathe to the atmosphere and closes it during leak tests of the fuel vapor system. P0498 sets when the control circuit voltage is lower than the control module expects, usually from a short to ground or a failing solenoid coil. As a result the module cannot reliably open or seal the vent.

Symptoms

  • Check engine light on
  • Fuel pump nozzle clicks off repeatedly while filling the tank
  • Faint fuel vapor smell
  • Failed EVAP or emissions inspection
  • Tank that stays pressurized or hisses when the cap is opened

Possible causes

  1. Failed vent valve solenoid
  2. Control wire shorted to ground
  3. Chafed or damaged wiring harness near the tank or canister
  4. Vent valve stuck mechanically
  5. Corroded or damaged valve connector
  6. Rarely, a faulty driver in the PCM

How to diagnose

  1. Scan for codes and freeze frame data, clear the code and see if it returns
  2. Check that the fuel cap seats properly and its seal is intact
  3. Inspect the vent valve, connector and harness for damage, moisture and corrosion
  4. Measure the solenoid coil resistance and compare it with the specification
  5. Command the valve on and off with a scan tool and confirm it clicks and actually seals
  6. Test the control circuit for a short to ground and for proper power supply
  7. Watch fuel tank pressure sensor readings while cycling the purge and vent valves
  8. Smoke-test the EVAP system for leaks if needed

Common fixes

  • Replace the EVAP vent valve
  • Repair or replace the damaged wiring and connector
  • Replace the charcoal canister if the valve is integrated or the canister is clogged
  • Replace the fuel cap if it no longer seals
  • Replace or reprogram the PCM only if it is confirmed faulty

Questions and answers

What does P0498 mean?

It means the control circuit of the EVAP vent valve reads low. The PCM cannot control the valve properly, most often because of a short to ground or a bad solenoid.

Can I drive with P0498?

Usually yes, it does not endanger the engine. It is still worth fixing soon because of possible fuel odor, refueling trouble and a failed emissions test.

How do I fix P0498?

Start by inspecting the valve wiring and connector, then check the solenoid resistance and its operation with a scan tool. Replacing the vent valve or repairing a shorted wire fixes most cases.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.