Technical Description of OBD-II Trouble Code
Flow of EVAP (evaporative emission) During a Non-Purge Condition
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
A quick search on the internet reveals that this code is more commonly found in GM (Chevy, Pontiac, etc.) vehicles. In Acura, Honda, Hyundai, Kia, and Mazda vehicles, this code is referred to as “EVAP system high purge flow,” which essentially means the same thing.
This DTC is designed to check for any undesired intake vacuum flow to the EVAP system. The control module ensures the sealing of the EVAP system by turning 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 there is any vacuum being drawn on the EVAP system.
If the vacuum in the EVAP system exceeds a predetermined value within a predetermined time, this code is triggered and the MIL (malfunction indicator lamp) is illuminated.
Signs and Symptoms
The symptoms of a P0496 DTC typically include the illumination of the Malfunction Indicator Lamp (MIL), and most likely no other noticeable symptoms. Some individuals may experience a hard start or crank condition. In certain cases, the engine may run rich, which may not be detected immediately but can cause long-term damage, such as catalytic converter damage.
Possible Causes
The potential causes of a P0496 EVAP code include:
(Hyundai, Isuzu)
Possible Solutions
The most common solution for this DTC is to replace the purge solenoid valve. However, it is important to conduct a proper diagnosis before replacing any parts!
Ideally, you should use an advanced scan tool with the ignition on and the engine off to seal the EVAP system using the Seal/Purge function. Then, observe the fuel tank pressure sensor reading when you turn off the purge. If the pressure value is higher than the normal range set by the manufacturer, it is recommended to replace the EVAP canister purge solenoid valve. Refer to a model-specific repair guide for the appropriate specifications.
If you do not have access to a scan tool, you can disconnect the vacuum line at the purge valve going back to the charcoal canister. Unplug the electrical connector on the purge valve, start the engine, and then place your finger on the valve where you disconnected the line. If you can feel vacuum there, it indicates that the purge solenoid valve is faulty and needs to be replaced. Alternatively, you can simply remove the purge solenoid valve and blow into it. It should normally be closed, so if air passes through, it indicates the need for replacement.
If the purge valve is functioning properly, either the problem with the valve is intermittent or there is an issue with the fuel tank pressure sensor. To test the fuel tank pressure sensor, you will need a high-end scan tool to monitor the tank pressure with the gas cap removed. If the sensor shows vacuum with the gas cap removed, it indicates a problem with the fuel tank pressure sensor.
Here is an image of a purge solenoid valve. Your valve may appear similar or different, so consult a factory service guide or your local vehicle dealership for more details:
