There are a lot of possible ways in which the evaporative emission system can malfunction in a vehicle. In case you didn’t know, this is the system which prevents fuel vapors from leaving your vehicle’s gas tank and entering the outside atmosphere. It is a very complex system which is comprised of fuel vapor pressure sensors, a charcoal canister, and a vapor pipe. The purge flow refers to how much fuel vapors flow into the engine. This is determined by how much air enters the system, thanks to the intake vacuum.
The engine control unit sets the value of the intake vacuum flow for the evaporative emission system. The charcoal in the canister is what stores the fuel vapors from the gas tank. In normal circumstances, the intake vacuum will cause air to flow to the charcoal canister. Once the air hits the canister, the stored fuel vapors will then flow into the engine. While flowing there, the purge valves will open so that the proper amount of fuel vapors can make it through. The engine control unit manages the purge solenoid and valve.
Trouble Code P0496
There are certain issues that can happen in the evaporative emission system which will cause the intake vacuum flow to increase much higher than normal. This means that more air will be let into the charcoal canister, causing an increase in the amount of fuel vapor heading toward the engine. This results in a “high purge flow” situation in the system. If you were to run a diagnostic check on the powertrain control module, the scanner will likely detect trouble code P0496. This is the specific code which refers to the high purge flow problem.
Of course, there are a lot of other possible causes which can be linked to a high purge flow and trouble code P0496. For instance, you could have bad electrical connections in your vehicle. You could also have a bad fuel pressure sensor, purge valve, vent valve, canister purge valve, or vent solenoid. In some cases, your charcoal canister might be plugged.
It is hard for a driver to notice a high purge flow problem because it is not exactly something that makes noise or creates something for you to see. The first symptom you will probably notice is your “Check Engine” light coming on. But there could be dozens of reasons for this light illuminating on the dashboard. You probably aren’t going to care too much if your car still functions properly. At the worst, you may have problems starting your engine if the vapors build up too much in the engine.