What Does It Mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
A quick online search shows this code appears more common with GM vehicles (Chevy, Pontiac, etc.). In Acura, Honda, Hyundai, Kia, and Mazda vehicles, this code is described as “EVAP system high purge flow,” which is the same thing.
This DTC checks for unwanted intake vacuum flow to the EVAP system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve OFF and the EVAP canister vent solenoid valve ON. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being developed in the EVAP system.
If the vacuum in the EVAP system exceeds a predetermined value within a set time, this code is set and the MIL (malfunction indicator lamp) illuminates.
Symptoms
Symptoms of a DTC P0496 include the MIL illuminating, and most likely no other noticeable symptoms. Some may experience hard starting. In some cases, the engine may run rich, which may not be noticeable but can cause long-term damage (e.g., catalytic converter damage).
Potential Causes
Potential causes of an EVAP P0496 code include:
- Faulty purge or vent solenoid valve
- Clogged EVAP canister
- Faulty EVAP/fuel tank pressure sensor
- Poor electrical connection
- Electrical short condition
- (Hyundai, Isuzu)
- Faulty canister purge valve
- Blocked vapor canister
- Faulty vent solenoid
- Leaking EVAP system hose (Hyundai)
- Faulty purge flow sensor (Kia, Mazda)
Possible Solutions
The most common solution for this DTC is to replace the purge solenoid valve. However, ensure proper diagnosis before replacing parts!
Ideally, use an advanced scan tool with the ignition on and engine off, seal the EVAP system using the Seal/Purge function. Then, observe the fuel tank pressure sensor reading when disabling the purge. If the pressure value is outside the manufacturer’s specified range, replace the EVAP canister purge solenoid valve. Refer to a model-specific repair guide for proper specifications.
If you don’t have access to a scan tool, you can disconnect the vacuum line at the purge valve toward the charcoal canister. Disconnect the electrical connector on the purge valve, start the engine, and place your finger over the valve where the line was disconnected. If you feel vacuum, the purge solenoid valve is faulty and needs replacement. Alternatively, you can remove the purge solenoid valve and blow through it. It is normally closed, so if air passes through, it should be replaced.
If the purge valve checks out fine, the issue with the valve is intermittent, or there’s a problem with the fuel tank pressure sensor. To test the fuel tank pressure sensor, you’ll need a high-end scan tool to monitor tank pressure with the gas cap removed. If the sensor shows vacuum with the gas cap off, there’s an issue with the fuel tank pressure sensor.