P1441 – Evaporative Emission (EVAP) System Flow During Non-Purge (Buick, Cadillac, Chevrolet, Dodge, GM, Isuzu, Pontiac, Saturn)

By Reinier (Contact Me)
Last Updated 2016-12-30
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1441

Table of Contents

1. What Does Code P1441 Mean?
2. What are the common causes of code P1441?
3. What are the symptoms of code P1441?
4. How do you troubleshoot code P1441?
5. Codes Related to P1441
6. Get Help with P1441

What Does Code P1441 Mean?

SPECIAL NOTES: In order to diagnose code P1441 – “Evaporative Emission (EVAP) System Flow During Non-Purge” correctly, non-professional mechanics are advised to read the section on the EVAP (Evaporative Emission Control System) in the manual for the application being worked on carefully, since some EVAP systems are pressurized during self-tests, while others are subjected to a strong vacuum during self-tests. For this reason, this guide cannot provide detailed diagnostic and repair information for code P1441 that will be valid for all applications under all conditions.

Therefore, the information provided here is intended for general informational purposes only, and it should NOT be used in any diagnostic procedure for this code without making proper reference to the manual for the application being worked on. However, the generic diagnostic and repair steps outlined in this guide should enable most non-professional mechanics to diagnose and repair code P1441 – “Evaporative Emission (EVAP) System Flow during Non-Purge” successfully on almost any application. END OF SPECIAL NOTES.

OBD II fault code P1441 is a manufacturer specific code that is defined by carmakers Acura, Citroen/Peugeot, GM, and Isuzu, among many others as “Evaporative Emission (EVAP) System Flow during Non-Purge”, and on these applications, code P1441 is set when the PCM (Powertrain Control Module) detects an undesired flow of fuel vapors through the EVAP system. Depending on the application, and the type of EVAP system fitted, this condition can occur either during a self-test procedure when the EVAP system should be in a sealed state, or at a time when the PCM has not commanded a purge of the EVAP system.

When an EVAP system is purged of fuel vapors, the vapors are fed into the engine in a controlled manner under very specific operating conditions to be combusted with the air/fuel mixture. This improves fuel economy, and at the same time, the process of purging fuel vapors reduces emissions. However, an uncontrolled purging of the EVAP system due to a failure of, or malfunction in a system component can cause driveability issues, an increase in fuel vapor emissions, and cause the vehicle to fail an emissions test.

Regardless of the design and operating principles of any given EVAP system, all EVAP systems have the purpose of capturing and containing fuel vapors before they can escape into the atmosphere to contribute to environmental pollution. To accomplish this, EVAP systems use a constellation of components that include flow control valves, control solenoids, vent valves, pressure and flow sensors, charcoal canisters in which to store fuel vapor temporarily, vacuum lines, a gas tight fuel filler cap, and in some cases, a dedicated air pump with which to pressurize the system for diagnostic purposes.

During a self-test, the PCM either pressurizes the EVAP system (depending on the application), or creates a vacuum in the system to test for leaks in the system. In both cases, this test is performed every time the vehicle is started, and in both the cases, the vacuum or pressure must be maintained for a time set by the manufacturer. If a leak in the system causes the vacuum to decay or the pressure to drop beyond a critical level within a set period of time, code P1441 will be set, and a warning light will illuminate. Take note however that code P1441 is only one of several possible codes that can be set when the system fails a self-test: in many cases, other EVAP related codes could be set along with P1441.

Having said all of the above though, code P1441 is more likely to be set without other codes when the PCM detects a flow of fuel vapors through the EVAP system at a time when there should not be a flow, as opposed to when the EVAP fails a self-test or fails to complete a readiness monitor. Regardless of the system design, to purge the system effectively the PCM opens a purge valve at the same time it opens a vent valve that allows fresh air to assist in displacing the fuel vapors from the charcoal canister.

When both valves are open, engine vacuum “sucks” the stored fuel vapors into the inlet manifold through a dedicated vacuum line. When exactly this happens depends on many factors and inputs from many sensors, but suffice to say that when the PCM deems the purging process to be complete, or that continued purging would be detrimental to the combustion process, it will close both the purge and vent valves, which in theory, should leave the EVAP system in a sealed state to prevent new fuel vapors from escaping into the atmosphere.

Therefore, if the purge valve does not close all the way, fuel vapor can continue to be sucked into the engine, even though the PCM “thinks” the purge valve is closed. This situation can be made worse if either (or both) the vent valve and fuel filer cap are also not sealing properly. If this happens, fuel vapor is “sucked” into the engine in a completely uncontrolled manner, which is the most likely cause of code P1441 – “Evaporative Emission (EVAP) System Flow during Non-Purge”.

The image below shows a simplified schematic of a typical EVAP system. Note that if the vent valve (as shown on this image) remains open while the purge valve is also open, an open circuit (arrowed lines), is created through which fuel vapors can be sucked into the engine in an uncontrolled manner through the throttle body.

What are the common causes of code P1441?

Typical common causes of P1441 could include the following-

• Defective purge control valve. (The most likely cause)
• Defective charcoal canister
• Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
• Leaks in vacuum lines
• Leaking fuel filler cap

NOTE: Be aware that the charcoal canisters on GM applications are particularly susceptible to damage caused by over filling the fuel tank.

What are the symptoms of code P1441?

Depending on the exact nature of the problem, and apart from a stored trouble code and an illuminated warning light, typical symptoms of P1441 could include the following-

• Drivability issues that could include varying degrees of power loss
• Rough idling
• Fluctuating idling speed
• Surging or hesitation upon hard acceleration
• Hard starting when the engine is hot
• Strong odor of fuel may be present in some cases
• Vehicle will almost certainly not pass an emissions test

How do you troubleshoot code P1441?

NOTE #1: Since not all EVAP system designs share all components, non-professional mechanics are strongly urged to familiarize themselves with the type of EVAP system fitted to the application being worked on before attempting a diagnosis and repair of this code.

NOTE #2: Apart from a repair manual for the application, a smoke machine and a hand-held vacuum gauge fitted with a gauge are required items to diagnose this code.

Step 1

Record all fault codes present, as well as all available freeze frame data. This information could be of use should an intermittent fault be diagnosed later on.

NOTE: While diagnosing EVAP related codes generally requires that the engine be in excellent running condition with no exhaust leaks, misfire-related codes, or engine vacuum system related codes being present, the nature of code P1441 is such that misfires are often a direct result of the code. For this reason, it is important to find and correct the cause(s) of code P1441 first, before attempting to resolve misfire codes that will likely resolve themselves once P1441 is resolved.

Step 2

Consult the manual to determine which type of EVAP system is in use on the application. If the EVAP system is pressurized for self-diagnostic purposes, there will be wiring and components present that are not present on systems that use a vacuum for self-diagnostic testing. For this reason, it is important to gain at least a basic understanding of how the EVAP on the application being worked on works and which components are therefore most likely to produce code P1441 on that application.

Step 3

Once the working principles of the EVAP system has been studied, consult the manual again to determine the location of all components, as well as the location, function, routing, and color-coding of all associated wiring, connectors, and vacuum lines. Note that on some applications, it may be necessary to remove splash covers and heat shields to gain access to wiring and vacuum lines.

NOTE: Inspecting EVAP system components is a lot easier when the vehicle can be lifted on a vehicle hoist. If a hoist is not available, jack the vehicle up as high off the ground as possible, and use approved jack stands to support vehicle during the diagnostic/repair process.

Step 4

Once all wiring and vacuum lines are fully accessible, perform a thorough visual inspection of all wiring, connectors, and vacuum lines. Look for damaged, burnt, disconnected, or corroded wiring and/or connectors. Make repairs as required, clear all codes, and retest the system to see if any codes return.

Pay particular attention to the wiring of the purge valve, since malfunctions in this circuit is a leading cause code P1441. Also, be sure to inspect all vacuum lines for signs of damage, perforations, splitting, cracking, or other damage that could conceivably influence the correct operation of the EVAP system. Resist the temptation to repair vacuum lines; the best option is to replace the entire vacuum line between factory joints to reduce the possibility of future problems.

Step 5

If no visible damage to vacuum lines and wiring is found, consult the manual to determine the correct procedure to test all wiring and components for resistance, reference voltages, ground connectivity, and continuity.

NOTE: Bear in mind that short-circuits in the purge valve wiring, as well as in the valve itself are common, but they are not always visible to a casual inspection. Therefore, pay particular attention to this valve and its wiring, since a short circuit can prevent it from closing.

Be sure also to test the resistance/continuity of all sensors as well, since all sensors form part of the EVAP control system. Compare all obtained readings with the values stated in the manual, and if discrepancies or deviations from stated values are found, make repairs as required, or replace components that do not comply with the manufacturers specifications. Retest all affected circuits/components after repairs/replacements are complete to verify that all electrical values fall within the manufacturer’s specifications. Clear all codes, and rescan the system to see if any codes return.

Step 6

If the code persists but all wiring and components check out OK, there are several ways to proceed from this point onwards. The way that will likely save the most time is to use the scanner to command the purge valve open, or if the scanner does not have control functions, to apply a current directly to the valve to open it, but be sure to follow the instructions in the manual on how to do this exactly to avoid damaging anything- including the PCM.

Next, prepare to fill the system with smoke (using the smoke machine) from the point where the EVAP system connects to the inlet manifold. The purge valve needs to be open for the smoke to fill the system, so allow a few minutes for the smoke to fill the system. Pay particular attention to the fuel filer cap- if any smoke escapes past it, air can enter the system past it as well, which will set code P1441. Replace the filler cap if any smoke is seen to escape past it.

Step 7

Bear in mind that it could take several minutes for small leaks in vacuum lines to reveal themselves, so do not assume that the system id gas tight if no leaks appear after a few seconds. Maintain the smoke in the system for at least five minutes. If after several minutes have elapsed no smoke appears anywhere to indicate leaks, it is almost certain that the purge valve is stuck open, or partly open.

To check if this is the case, remove the purge valve from the vehicle for further testing. This valve is normally closed, so attach the vacuum pump to one opening, and draw a vacuum, but be sure not to exceed the vacuum value stated in the manual for this test. If the vacuum holds steady for at least 30 seconds and the test equipment is not defective in any way, it is likely that the problem was caused by an intermittent or transient fault, or that charcoal granules from a defective charcoal canister had temporarily prevented the valve from closing.

If this is suspected, remove the charcoal canister from the vehicle, and shake it vigorously. This will often let charcoal granules fall out, which is evidence of a defective canister. Replacement of the canister is the only remedy. However, if the charcoal canister is defective, it is likely that charcoal granules have entered the vacuum line between the canister and the purge valve. This can only be fixed either by replacing the vacuum line, or by using strong compressed air to force all charcoal granules from the line.

NOTE: Of course, if the vacuum does not hold across the purge valve, no matter how slowly it decays the purge valve is defective, and it must be replaced.

Step 8

In nine out of every ten instances of code P1441, the diagnostic/repair steps outlined up to this point will resolve the issue, and especially if both the charcoal canister and the purge valve are replaced.  However, if the code persists despite repeated repair attempts, it is likely that an intermittent electrical fault or other transient problem such as migrating charcoal granules is causing the code to return. The only reliable remedy in these cases is to remove and clean out all vacuum lines, or to allow the electrical fault to worsen until an accurate diagnosis and definitive repair can be made.

Step 9

If code P1441 does not immediately return after repairs or replacements are complete, be sure to perform (and complete) at least two drive cycles as per the manufacturer’s instructions to verify that repairs had been successful, since on most applications, two consecutive failures of the EVAP system are required before code P1441 will set.

Codes Related to P1441

There are no codes that are directly related to P1441: however, other manufacturer specific codes, as well as several generic codes can contribute to P1441 being set. Refer to the manual for the application being worked on for detailed information on additional codes that could be present along with P1441 on that application.

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