Engine Troubleshoot

P0441 Evaporative Emission Control System Incorrect Purge Flow

Evaporative Emission Control System Incorrect Purge Flow

What Is Engine Code P0441?

  • P0441 Technical Definition: ​Evaporative Emission Control System Incorrect Purge Flow
  • P0441 Meaning: EVAP purge flow is not detected
  • Most common cause: Faulty fuel tank vacuum switch or EVAP purge solenoid
  • Risks for the engine/driver: LOW It should be safe to drive the car, but you should get it checked out by a mechanic ASAP
  • Emissions severity: HIGH. The car won’t pass the emissions testing
  • Estimated repair time: 1 day
  • Estimated repair cost: $200-$500

The engine code P0441 is stored in memory when the ECU detects a malfunction in the Evaporative Emission System (EVAP) purge flow.

The EVAP is an integral part of the emissions control system, its role is preventing fuel fumes from reaching the atmosphere. These gases are the normal result of fuel evaporating inside the tank. The EVAP system consists of a sealed container (fuel tank) that works in conjunction with one or more charcoal canisters that purge the gases back to the engine when the ECU consider it appropriate.

Besides controlling the EVAP purge and vent solenoids the ECU has a dedicated fuel tank pressure sensor (FTP sensor), a vacuum switch to detect purge flow and in some vehicles a leak detection pump. 

The P0441code is recorded when the ECU senses, through the EVAP vacuum switch, that no purge flow occurs when it is commanded.

2 Common Symptoms When Code P0441 is Present

  1. Check Engine Light lit.
  2. Gasoline smell coming from the vehicle

Possible Causes For P0441

  1. Purge solenoid wiring (open, shorted, burnt) 
  2. Purge solenoid connector (loosely, corroded, disconnected or bent pins)
  3. EVAP vacuum switch wiring (open, shorted, burnt) 
  4. EVAP vacuum switch connector (loosely, corroded, disconnected or bent pins)
  5. Burnt, damaged, broken or deteriorated EVAP hose.
  6. Defective fuel tank seal.
  7. Defective EVAP canister.

How To Diagnose The Cause Of P0441

For the purpose of this article, it’s assumed that you have a basic knowledge of safety precautions while working on your vehicle.

Always refer to the appropriate OEM literature when possible. Original manufacturer diagnostic procedures should always have precedence over a generic workflow.

That said, let’s start the diagnostic process!

1. Preliminary steps

To discard a possible intermittent DTC condition, you’ll need to clear the ECU memory and complete a driving cycle.

  • Read data trouble codes and take note of them.
  • Clear data trouble codes memory.
  • Perform a driving cycle (at least 5-10 minutes).

In case the Check Engine Light stays off then you may have an intermittent problem. If the light lit during your driving cycle then continue with the diagnostic process.

2. Visual Inspection

> Vacuum Switch inspection: perform a meticulous visual inspection of the fuel tank vacuum switch wiring and connectors. Look for burnt, damaged, corroded or deteriorated wires, also unplug the switch and look for bent terminal pins, loosely connections, corrosion or any other possible indication of a bad connection.

> EVAP hoses: perform a meticulous visual inspection of all Evaporative Emission system hoses. These hoses come from the fuel tank all the way through the EVAP canisters and then from the canister they go to the intake manifold. Check for loose clamps, deteriorated hoses, etc. Don’t overlook this step. Many times the code P0441 is caused by a large leak in one of these hoses.

Fix any wiring problem before continuing.

3. Scan Tool Tests

> Fuel Tank Pressure sensor test: for this test, you will need to access the fuel pump assembly. Depending on your vehicle this could be as easy as removing the rear seat row but in some cases, you may need to remove the fuel tank which isn’t an easy task. Please keep that in mind before starting the test.

Assuming you have access to the sensor, remove it from the fuel pump assembly. This sensor is like the Manifold Absolute Pressure sensor (MAP). Turn the ignition key on (engine off). Using the relevant adapter connect a manual vacuum pump to the sensor port. Now you can increase the pressure (positive pressure) or create a light vacuum using the manual pump.

With the help of a scan tool, watch the sensor output as you vary the pressure. If no change is detected then you should check the wiring from the sensor to the ECU. This is an analog sensor, start verifying the 5V reference voltage and ground. An alternative method that doesn’t require accessing the fuel pump assembly is disconnecting one of the fuel vapor vent lines. You can pressurize/depressurize the tank through that hose using a manual vacuum pump. Never use compressed air for this task because is highly dangerous.

> EVAP solenoids functional test: start the engine to enter KOER mode. Depending on the year and maker of your vehicle you may have access to EVAP functional tests. The functional test consists in opening/closing the EVAP purge. If the solenoids are not working then you should check the wiring, connector, relay, and fuse.

> EVAP leak detection pump functional test: start the engine to enter KOER mode. Depending on the year and maker of your vehicle you may have access to EVAP functional tests. This functional test consists of operating the EVAP leak detection pump. If the pump is not working then you should check the wiring, connector, relay, and fuse. Replace as necessary.

How To Repair Error Code P0441

Depending on the diagnostics results you may need to do the following:

  • Replace the fuel tank vacuum switch
  • Replace or repair the EVAP hoses
  • Replace the fuel tank pressure sensor (FTP)
  • Replace the EVAP leak detection pump
  • Replace or repair the purge solenoids, relay or fuse.

It's important not to ignore any smell of fuel from your car.

A fuel vapor in the cabin of your car can be dangerous, and it's usually an  instant fail of any emissions tests.

Even when this code doesn’t affect engine’s performance you need to be aware of legal issues when driving in zones with strict emissions regulations.

Last Updated on 01/21/2020 by The Motor Guy