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Evaporative Emission Control System Incorrect Purge Flow


The code P0441 means that the Evaporative control system purge flow is incorrect. First, let's quickly review what the Evaporative control system is. The Evaporative control system (EVAP) prevents gasoline vapors from the fuel tank from escaping into the atmosphere. The Evaporative control system catches and stores gasoline vapors in a small box installed near the fuel tank called charcoal canister. When you drive and certain conditions (speed, engine temperature, etc.) are met, fuel vapors are gradually purged from the charcoal canister and burned inside your engine. The code P0441 means that the purge flow is lower or higher than it should be in these conditions. The purge flow is controlled by the purge valve (purge solenoid).

Symptoms:

Other than the Check Engine light, there might be no driveability symptoms or the engine may surge or run a little rough at idle.

Common causes:

- bad purge valve
- clogged or disconnected purge line
- vacuum leak near the purge line /engine intake connection
- bad vapor pressure sensor
- damaged or cracked charcoal canister
- faulty leak detection pump (LDP)
- bad NVLD unit (Chrysler)
- sticking or faulty vent valve
- cracked or clogged EVAP VSV vacuum hoses (Toyota)
- bad EVAP VSV valve (Toyota)
- misrouted vacuum hoses
- open or short in the purge valve control wiring
- rusted filler neck (rust belt states)

How the code p0441 is diagnosed:

Without a scan-tool: The first part is to check visually for obvious problems: if the gas cap closed properly, there is no cracks or other damage on the charcoal canister and all vacuum hoses related to the EVAP system are properly connected. If no obvious problem is found, the purge valve needs to be tested next. The purge valve should be normally closed. It opens when voltage is applied to its terminals. The purge valve is typically tested with a hand-held vacuum pump. It should hold the vacuum when closed (no voltage) and open fully when voltage is applied; see the procedure below. Sometimes the purge valve may be sticking intermittently but work properly when tested. If there is any suspicion, the purge valve must be replaced; usually it's not very expensive.
If there are other codes, such as P0446 or P0442, they need to be checked out first, as the P0441 can be triggered by the same fault.
With a scan tool: The manufacturer-specific scan tools usually have capability to run the test of the whole EVAP system. With a generic scan tool, the purge valve must be activated and the EVAP system pressure monitored.



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